Searches and Seizures at the Border and the Fourth Amendment

Searches and Seizures at the Border and the Fourth Amendment

Searches and Seizures at the Border and the
March 30, 2021
Fourth Amendment
Hillel R. Smith
Congress has broad authority to regulate persons or items entering the United States, an authority
Legislative Attorney
that is rooted in its power to regulate foreign commerce and to protect the integrity of the nation’s

borders. Exercising this authority, Congress has established a comprehensive framework that
Kelsey Y. Santamaria
authorizes federal law enforcement officers to inspect and search persons and property at the
Legislative Attorney
border to ensure that their entry conforms with governing laws, including those relating to

customs and immigration.

While federal statutes confer substantial authority to conduct border searches, this authority is not
absolute. The Fourth Amendment to the U.S. Constitution forbids unreasonable government searches and seizures of “the
people,” and this limitation extends to searches conducted at the border. The touchstone of the Fourth Amendment is the
reasonableness of a search. The Supreme Court has recognized that searches at the border are “qualitatively different” from
those occurring in the interior of the United States, because persons entering the country have less robust expectations of
privacy, given the federal government’s broad power to safeguard the nation by examining persons seeking to enter its
territory. While law enforcement searches and seizures within the interior of the United States typically require a judicial
warrant supported by probable cause, federal officers may conduct routine inspections and searches of persons attempting to
cross the international border without a warrant or any particularized suspicion of unlawful activity. But a border search that
extends beyond a routine search and inspection may require at least reasonable suspicion. The Supreme Court has not
precisely defined the scope of a routine border search, but has suggested that highly intrusive searches may fall outside that
category and thus require heightened suspicion to withstand Fourth Amendment scrutiny. Thus, the Court has held that the
prolonged detention of an airplane traveler pending invasive medical tests required reasonable suspicion that the traveler was
a drug smuggler. Conversely, the Court has determined that the removal and disassembly of a fuel tank constituted a routine
border search where reasonable suspicion of unlawful activity was not required.
The Supreme Court and lower courts have applied this border search exception not only to the physical border itself, but also
to searches at the border’s “functional equivalent,” such as at a port of entry in the interior of the United States (e.g., an
international airport). Border-related searches and seizures in areas beyond the border or its functional equivalent are
generally subject to greater Fourth Amendment scrutiny. For example, government officers may conduct warrantless
“extended border searches” of individuals found within the United States if there is both reasonable certainty of a recent
border crossing and reasonable suspicion of unlawful activity. Government officers may also conduct certain warrantless
searches near the border that do not require evidence of a border crossing. For instance, “roving patrol” stops of vehicles near
the border to question the vehicle’s occupants are permissible if there is reasonable suspicion of unlawful activity, while
probable cause is required to search the vehicle for contraband or other evidence of a crime. And while vehicle stops at fixed
immigration checkpoints are permissible without individualized suspicion, government officers must have probable cause to
search vehicles at those checkpoints. In addition, government officers may board vessels in interior or coastal waterways to
conduct routine document and safety inspections, but may require at least reasonable suspicion to conduct more intrusive
searches of the vessel.
Recent years have seen legal challenges to border searches of electronic devices such as cell phones and computers, which
often contain more personal and sensitive information than other items frequently searched at the border, such as a wallet or
briefcase. The Supreme Court has not yet addressed this issue. Lower courts have generally held that government officers
may conduct relatively limited, manual searches of such devices without a warrant or any particularized suspicion. The
courts, however, are split over whether more intrusive, forensic searches require at least reasonable suspicion. Additionally,
there is some debate over warrantless drone surveillance at the border and surrounding areas, given a drone’s potential
capability to access more information about a person than other forms of aerial surveillance. Another emerging issue
concerns the use of biometrics, particularly the collection of DNA samples from detained aliens at the border. Apart from
these issues, there have also been concerns about the use of “racial profiling” during investigatory stops near the border.
Legislation introduced in recent Congresses would clarify the government’s ability to conduct searches and seizures at the
border and surrounding regions.

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Contents
Constitutional Authority Over the Border ....................................................................................... 3
Federal Statutory and Regulatory Framework for Searches and Seizures at or Near the
Border ........................................................................................................................................... 4
Federal Customs Statutes and Regulations ............................................................................... 5
Customs Officers’ Authority ............................................................................................... 5
Coast Guard Authority ........................................................................................................ 7
Federal Immigration Laws and Regulations ............................................................................. 7
Border Searches and the Fourth Amendment ................................................................................ 12
General Overview of the Fourth Amendment ......................................................................... 12
“The People” Protected by the Fourth Amendment .......................................................... 13
Searches ............................................................................................................................ 16
Seizures ............................................................................................................................. 17
Standards of Suspicion: Probable Cause and Reasonable Suspicion ................................ 18
Warrantless Searches and Seizures ................................................................................... 19
Searches at International Borders ............................................................................................ 19
The Border and Its Functional Equivalent ........................................................................ 20
Searches and Seizures: Routine and Nonroutine .............................................................. 21
Other Exceptions to the Fourth Amendment’s Warrant Requirement That May Be
Relevant to Encounters Near the Border .............................................................................. 25
Warrantless Arrests ........................................................................................................... 27
Government Searches Beyond the Border and Its Functional Equivalent .................................... 28
Extended Border Searches ...................................................................................................... 28
Boarding and Inspection of Vessels Within Interior and Coastal Waterways ......................... 31
United States v. Villamonte-Marquez ............................................................................... 32
Lower Courts’ Decisions on Boarding of Vessels ............................................................. 33
Roving Patrols ......................................................................................................................... 34
Almeida-Sanchez v. United States .................................................................................... 35
United States v. Brignoni-Ponce ....................................................................................... 35
United States v. Cortez ...................................................................................................... 37
United States. v. Arvizu .................................................................................................... 37
Lower Court Decisions on Roving Patrols ....................................................................... 38
Fixed Immigration Checkpoints .............................................................................................. 39
United States v. Martinez-Fuerte ...................................................................................... 40
United States v. Ortiz ........................................................................................................ 41
Lower Court Decisions on Immigration Checkpoints ...................................................... 42
Transportation Checks ............................................................................................................. 44
Select Legal Issues ........................................................................................................................ 45
Border Searches of Electronic Devices ................................................................................... 45
Riley v. California ............................................................................................................. 46
Lower Courts’ Application of the Border Search Exception to Electronic Device
Searches ......................................................................................................................... 46
Current CBP Policies on Electronic Device Searches ...................................................... 48
Drone Surveillance .................................................................................................................. 49
Biometric Data Collection at the Border ................................................................................. 52
Racial Profiling ....................................................................................................................... 55
Recent Legislation Concerning the Government’s Border Search Authority ............................... 59
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Figures
Figure 1. Area Within 100 Air Miles of the U.S. Border .............................................................. 10

Tables

Table A-1. Federal Statutes Authorizing Warrantless Customs Searches and Boarding of
Vessels ........................................................................................................................................ 61
Table A-2. Federal Statutes Authorizing Warrantless Searches and Seizures by
Immigration Officers .................................................................................................................. 63
Table A-3. Judicial Requirements for Border-Related Searches and Seizures .............................. 65

Appendixes
Appendix. ...................................................................................................................................... 61

Contacts
Author Information ........................................................................................................................ 67

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ongress has broad authority to regulate persons or items entering the United States, an
authority rooted in its power to regulate foreign commerce and to protect the integrity of
C the nation’s borders.1 Acting through this authority, Congress has established a
comprehensive framework that allows federal government officers to conduct searches and
seizures of persons and property at or near the international border.2 Under federal statutes,
government officers may inspect and search individuals, merchandise, vehicles, and vessels that
are attempting to enter the United States or found further within the interior of the country shortly
after entry, including to investigate customs violations and other breaches of federal law.3
Additionally, government officers have statutory authority to investigate potential violations of
federal immigration laws at the border and surrounding areas.4
There are constitutional constraints on the government’s power. The Fourth Amendment to the
Constitution protects against unreasonable searches and seizures by government officers.5
Generally, the Fourth Amendment requires an officer to obtain a judicial warrant based on
probable cause before arresting or searching an individual.6 The “touchstone” of the Fourth
Amendment is reasonableness, and the reasonableness of a government search may be
determined by balancing an individual’s privacy expectations with the legitimate government
interests supporting the search.7 Thus, courts have recognized “reasonable exceptions” where the
government may engage in a warrantless arrest or search.8 For example, the government may

1 See United States v. Montoya de Hernandez, 473 U.S. 531, 538 (1985) (recognizing “Congress’ power to protect the
Nation by stopping and examining persons entering this country”); United States v. 12,200-Foot Reels of Super 8mm.
Film, 413 U.S. 123, 125 (1973) (“The Constitution gives Congress broad, comprehensive powers ‘(t)o regulate
Commerce with foreign Nations.’ Historically such broad powers have been necessary to prevent smuggling and to
prevent prohibited articles from entry.”) (quoting U.S. CONST. art. I, § 8, cl. 3.).
2 See Montoya de Hernandez, 473 U.S. at 537 (“Since the founding of our Republic, Congress has granted the
Executive plenary authority to conduct routine searches and seizures at the border, without probable cause or a warrant,
in order to regulate the collection of duties and to prevent the introduction of contraband into this country.”); United
States v. Ramsey, 431 U.S. 606, 616 (1977) (noting that Congress recognized its “plenary customs power” by enacting
the first customs statute in 1789).
3 14 U.S.C. § 522; 19 U.S.C. §§ 482, 1467, 1496, 1581, 1583.
4 8 U.S.C. § 1357.
5 Specifically, the Fourth Amendment provides that, “[t]he right of the people to be secure in their persons, houses,
papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but
upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the
persons or things to be seized.” U.S. CONST. amend. IV. This limitation applies to state officers through the Fourteenth
Amendment. Mapp v. Ohio, 367 U.S. 643, 655 (1961) (observing that the Fourth Amendment’s prohibition against
unreasonable searches and seizures extends to the states through the Due Process Clause of the Fourteenth
Amendment).
6 See Riley v. California, 134 S. Ct. 2473, 2482 (2014) (“Such a warrant ensures that the inferences to support a search
are ‘drawn by a neutral and detached magistrate instead of being judged by the officer engaged in the often competitive
enterprise of ferreting out crime.’ ”) (quoting Johnson v. United States, 333 U.S. 10, 14 (1948)); Kentucky v. King, 563
U.S. 452, 459 (2011) (“Although the text of the Fourth Amendment does not specify when a search warrant must be
obtained, this Court has inferred that a warrant must generally be secured.”).
7 United States v. Knights, 534 U.S. 112, 118–19 (2001) (“The touchstone of the Fourth Amendment is reasonableness,
and the reasonableness of a search is determined ‘by assessing, on the one hand, the degree to which it intrudes upon an
individual’s privacy and, on the other, the degree to which it is needed for the promotion of legitimate governmental
interests.’ ”) (quoting Wyoming v. Houghton, 526 U.S. 295, 300 (1999)).
8 King, 563 U.S. at 459 (“Because ‘the ultimate touchstone of the Fourth Amendment is “reasonableness” ’. . . [t]he
warrant requirement is subject to certain reasonable exceptions.”) (quoting Brigham City, Utah v. Stuart, 547 U.S. 398,
403 (2006)); Texas v. Brown, 460 U.S. 730, 735 (1983) (“Our cases hold that procedure by way of a warrant is
preferred, although in a wide range of diverse situations we have recognized flexible, common-sense exceptions to this
requirement.”).
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bypass the warrant requirement if an arrest occurs in public and is based on probable cause or if a
search is incident to a lawful arrest.9 Additionally, warrantless searches and seizures of limited
duration and intrusion, such as a “stop and frisk” of a person suspected of wrongdoing, may be
permitted under a less exacting standard than probable cause, instead requiring only reasonable
suspicion of unlawful activity.10
Citing Congress’s constitutionally enumerated power to regulate foreign commerce and the
federal government’s inherent sovereign authority to protect the nation’s borders, the Supreme
Court has held that federal law enforcement officers may engage in routine inspections and
searches at the U.S. border without a warrant, probable cause, or reasonable suspicion.11 This
“border search exception” applies in circumstances when a person is attempting to enter or is
suspected to have entered the United States at the international border.12 Federal appellate courts
have construed the border search exception as applying equally to searches of persons departing
the United States.13 The exception applies not only to the physical border itself, but also to
searches at the border’s “functional equivalent,” such as at an international airport within the
United States.14
Yet the Fourth Amendment places some limits on the government’s border search authority. The
border search exception applies at the border or its functional equivalent; searches and seizures
further into the country’s interior may require at least heightened suspicion or probable cause of

9 See Davis v. United States, 564 U.S. 229, 232 (2011) (“[A] police officer who makes a lawful arrest may conduct a
warrantless search of the arrestee’s person and the area ‘within his immediate control.’ ”) (quoting Chimel v. California,
395 U.S. 752, 763 (1969)); United States v. Watson, 423 U.S. 411, 418 (1976) (“The cases construing the Fourth
Amendment thus reflect the ancient common-law rule that a peace officer was permitted to arrest without a warrant for
a misdemeanor or felony committed in his presence as well as for a felony not committed in his presence if there was
reasonable ground for making the arrest.”).
10 See Terry v. Ohio, 392 U.S. 1, 21–22 (1968) (requiring “stop and frisk” of suspect to be predicated on “specific and
articulable facts,” rather than “unparticularized suspicion or hunch,” that “taken together with rational inferences from
those facts, reasonably warrant that intrusion.”).
11 See United States v. Flores-Montano, 541 U.S 149, 152–53 (2004) (“Time and again, we have stated that ‘searches
made at the border, pursuant to the longstanding right of the sovereign to protect itself by stopping and examining
persons and property crossing into this country, are reasonable simply by virtue of the fact that they occur at the
border.’ ”) (quoting United States v. Ramsey, 431 U.S. 606, 616 (1977)); United States v. Montoya de Hernandez, 473
U.S. 531, 538 (1985) (“Routine searches of the persons and effects of entrants are not subject to any requirement of
reasonable suspicion, probable cause, or warrant[.]”).
12 See Flores-Montano, 541 U.S. at 152 (reasoning that the government has broad authority to conduct routine searches
at the border because “[t]he Government’s interest in preventing the entry of unwanted persons and effects is at its
zenith at the international border.”); Ramsey, 431 U.S. at 619 (observing that border searches are characterized by the
fact that “the person or item in question had entered into our country from outside.”). See also D.E. v. Doe I, 834 F.3d
723, 727 (6th Cir. 2016) (search of motorist’s vehicle was lawful under the border search exception, even though the
motorist claimed to have arrived at the international border inadvertently and intended to turn around).
13 See, e.g., United States v. Odutayo, 406 F.3d 386, 391–92 (5th Cir. 2005) (holding border search exception applies to
outgoing baggage); United States v. Boumelhem, 339 F.3d 414, 419–20 (6th Cir. 2003) (establishing that border search
exception applies to outgoing cargo container); United States v. Beras, 183 F.3d 22, 26 (1st Cir. 1999) (concluding that
pat down of outgoing traveler was permitted under the border search exception).
14 Montoya de Hernandez, 473 U.S. at 538 (international airport); Ramsey, 431 U.S. at 622 (post office receiving
international mail); Almeida-Sanchez v. United States, 413 U.S. 266, 272–73 (1973) (describing the border’s functional
equivalent to include an international airport or “an established station near the border, at a point marking the
confluence of two or more roads that extend from the border”); United States v. Stewart, 729 F.3d 517, 525 (6th Cir.
2013) (international airport).
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unlawful activity.15 Moreover, a border search extending beyond a routine search may require at
least reasonable suspicion of criminal activity to withstand Fourth Amendment scrutiny.16
This report examines the statutory framework for border searches and seizures and the
constitutional constraints that must inform the exercise of this statutory authority. The report first
surveys federal statutes and regulations authorizing government officers to conduct warrantless
searches and seizures at the border and surrounding areas. The report then discusses the Fourth
Amendment’s general limitations on government searches and seizures. The report next examines
the border search exception and the extension of that exception further into the interior of the
United States, such as at immigration checkpoints on roads near the border. The report also
discusses several emerging border-related Fourth Amendment issues, including electronic device
searches at the border, drone surveillance, the collection of biometric data, and racial profiling.
Finally, the report reviews recent legislation concerning the government’s border search authority.
Constitutional Authority Over the Border
The Supreme Court has long recognized the authority of government officials to perform searches
and seizures at international borders.17 The Court has traced this federal power to two sources: (1)
the United States’ inherent sovereignty as a nation-state;18 and (2) the Constitution’s Foreign
Commerce Clause.19
By establishing a federal government, the Constitution was understood to confer upon it all the
powers incident to the United States’ existence as a sovereign, independent nation—including
unqualified authority over the nation’s borders and ability to determine whether foreign nationals
may come within its territory.20 The Supreme Court has repeatedly recognized that principles of

15 See United States v. Martinez-Fuerte, 428 U.S. 543, 562 (1976) (holding that routine checkpoint stops near the
border do not require any individualized suspicion); United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975)
(“Except at the border and its functional equivalents, officers on roving patrol may stop vehicles only if they are aware
of specific articulable facts, together with rational inferences from those facts, that reasonably warrant suspicion that
the vehicles contain aliens who may be illegally in the country.”); Almeida-Sanchez, 413 U.S. at 273 (holding that
“roving patrol” search of automobile more than 20 miles north of the U.S.-Mexico border required probable cause or
consent); Alfonso, 759 F.2d at 734 (requiring reasonable suspicion for extended border searches occurring subsequent
to a border crossing).
16 See Flores-Montano, 541 U.S. at 152–54, 156 (suggesting that “highly intrusive” searches of a person or
“destructive” searches of property may require a heightened level of suspicion); Montoya de Hernandez, 473 U.S.
at 541 (“We hold that the detention of a traveler at the border, beyond the scope of a routine customs search and
inspection, is justified at its inception if customs agents, considering all the facts surrounding the traveler and her trip,
reasonably suspect that the traveler is smuggling contraband in her alimentary canal.”).
17 See, e.g., Montoya de Hernandez, 473 U.S. at 537; Ramsey, 431 U.S. at 616; Carroll v. United States, 267 U.S. 132,
154 (1925).
18 See, e.g., Ramsey, 431 U.S. at 616 (“That searches made at the border, pursuant to the long-standing right of the
sovereign to protect itself by stopping and examining persons and property crossing into this country, are reasonable
simply by virtue of the fact that they occur at the border, should, by now, require no extended demonstration.”);
Carroll, 267 U.S. at 154.
19 Ramsey, 431 U.S. at 619.
20 See, e.g., Chae Chan Ping v. United States, 130 U.S. 581, 609 (1889) (recognizing “[t]he power of exclusion of
foreigners” as “an incident of sovereignty belonging to the United States as a part of those sovereign powers delegated
by the constitution”); Nishimura Ekiu v. United States, 142 U.S. 651, 659 (1892) (“It is an accepted maxim of
international law that every sovereign nation has the power, as inherent in sovereignty, and essential to self-
preservation, to forbid the entrance of foreigners within its dominions, or to admit them only in such cases and upon
such conditions as it may see fit to prescribe.”); see also United States v. Curtiss-Wright, 299 U.S. 304, 318 (1936)
(“The power to acquire territory by discovery and occupation, the power to expel undesirable aliens, the power to make
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sovereignty include giving the federal government the power to regulate items and persons
entering U.S. territory.21 The Court has explained: “It is axiomatic that the United States, as
sovereign, has the inherent authority to protect, and a paramount interest in protecting, its
territorial integrity.”22 The Court observed in dicta in Carroll v. United States that “[t]ravelers
may be stopped in crossing an international boundary because of national self-protection
reasonably requiring one entering the country to identify himself as entitled to come in, and his
belongings as effects which may be lawfully brought in.”23
Authority to search items and persons at international borders has also been traced to the Foreign
Commerce Power, which grants Congress broad authority to regulate commerce with foreign
nations.24 The Court has described searches at the international border as “necessary to prevent
smuggling and to prevent prohibited articles from entry.”25
Federal Statutory and Regulatory Framework for
Searches and Seizures at or Near the Border
Federal statutes and implementing regulations confer designated law enforcement officers with
broad authority to conduct searches and seizures at the border and surrounding areas without a
warrant. These searches commonly occur at designated ports of entry along the border, such as
border crossing points.26 But searches may also occur in other places along or near the border.27
To enforce U.S. customs laws, federal law enforcement officers may inspect and search
individuals, merchandise, vehicles, and vessels arriving at the border, as well as further into the
interior of the United States and within U.S. waters. In addition, federal officers may detain and

such international agreements as do not constitute treaties in the constitutional sense, none of which is expressly
affirmed by the Constitution, nevertheless exist as inherently inseparable from the conception of nationality.”).
21 See, e.g., Ramsey, 431 U.S. at 616 (“That searches made at the border, pursuant to the long-standing right of the
sovereign to protect itself by stopping and examining persons and property crossing into this country, are reasonable
simply by virtue of the fact that they occur at the border, should, by now, require no extended demonstration.”);
Carroll, 267 U.S. at 154. Sovereignty, as a general principle, stems from a global recognition of international rules
governing the authority of a nation-state and its interactions with other nation-states. Sarah H. Cleveland, Powers
Inherent in Sovereignty: Indians, Aliens, Territories and the Nineteenth Century Origins of Plenary Power over
Foreign Affairs, 81 TEX. L. REV. 1, 15 (2002); see also Curtiss-Wright, 299 U.S. at 318 (“As a member of the family of
nations, the right and power of the United States in that field are equal to the right and power of the other members of
the international family.”).
21 Ramsey, 431 U.S. at 619.
22 United States v. Flores-Montano, 541 U.S. 149, 153 (2004).
23 Carroll, 267 U.S. at 154; see also Boyd v. United States, 116 U.S. 616 (1886).
24 U.S. CONST. art. I, § 8, cl. 3 (granting Congress “the power . . . [t]o regulate Commerce with foreign Nations[.]”).
25 United States v. Montoya de Hernandez, 473 U.S. 531, 537–38 (1985) (involving an individual stopped at airport
suspected of smuggling narcotics).
26 See United States v. Cotterman, 709 F.3d 952, 961–62 (9th Cir. 2013) (describing a “border search” as one that
occurs at ports of entry where there is an actual or attempted border crossing); U.S. CUSTOMS AND BORDER
PROTECTION, Border Security: At Ports of Entry (last modified Apr. 2, 2018), https://www.cbp.gov/border-
security/ports-entry (describing U.S. Customs and Border Protection’s functions at ports of entry).
27 See United States v. Villamonte-Marquez, 462 U.S. 579, 593 (1983) (recognizing the government’s interest in
patrolling inland or coastal waters “where the need to deter or apprehend smugglers is great”); Almeida-Sanchez v.
United States, 413 U.S. 266, 268 (1973) (noting that the Border Patrol conducts inland surveillance activities “all in the
asserted interest of detecting the illegal importation of aliens.”); U.S. Customs & Border Prot., Border Security: Along
U.S. Borders (Jan. 17, 2018), https://www.cbp.gov/border-security/along-us-borders (describing the Border Patrol’s
responsibilities along the border).
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search individuals and their vehicles at or near the border to enforce federal immigration laws.
Federal officers may also enforce other laws relating to the border, including federal statutes
concerning transnational criminal activity (e.g., gang activity), the introduction of harmful plant
or animal species, and public health requirements.28
Federal Customs Statutes and Regulations
Title 19 of the U.S. Code regulates commerce and the flow of goods into the United States.29 It
authorizes customs officers to inspect and search individuals and their personal belongings,
merchandise, vehicles, vessels, and other means of transport for the purpose of searching for
contraband and other violations of federal customs laws.30 This authority is encompassed in
various federal statutes, some of which are overlapping in scope. U.S. Customs and Border
Protection (CBP), a component of the Department of Homeland Security (DHS),31 is the federal
agency mainly responsible for enforcing customs laws.32 The U.S. Coast Guard also has customs
enforcement authority.33
Customs Officers’ Authority
Under 19 U.S.C. § 1496, a customs officer34 may examine “the baggage of any person arriving in
the United States in order to ascertain what articles are contained therein” and whether those
items are subject to taxes or otherwise prohibited.35 Similarly, 19 U.S.C. §1467 allows customs
officers to inspect and search the persons, baggage, and merchandise arriving by vessel from a
foreign port (including U.S. territories).36 Federal regulations also state that “[a]ll persons,

28 See, e.g., U.S. Immigr. & Customs Enf’t, Homeland Security Investigations (Aug. 15, 2019),
https://www.ice.gov/hsi; U.S. Customs & Border Prot., Protecting Agriculture (June 10, 2019),
https://www.cbp.gov/border-security/protecting-agriculture.
29 See 19 U.S.C. §§ 1–4732.
30 See id. §§ 482, 1467, 1496, 1499, 1581, 1582, 1583. Certain diplomatic officers and their families are exempted from
Title 19’s search authority. 19 C.F.R. § 148.82.
31 DHS’s predecessor agency, the former Immigration and Naturalization Service (INS), ceased to exist as an
independent agency under the U.S. Department of Justice in 2003, and its functions were transferred to DHS. See
Homeland Security Act of 2002, Pub. L. No. 107-296, §§ 101, 441, 451, 471, 116 Stat. 2135, 2142, 2192, 2195, 2205
(2002).
32 See 6 U.S.C. § 202 (delegating to the Secretary of Homeland Security responsibility for “administering the customs
laws of the United States.”); id. § 211(c) (authorizing the CBP Commissioner to regulate the flow of travelers and
goods entering or exiting the United States, and to enforce customs and trade laws). DHS assumed responsibilities that
were transferred from various federal agencies. See id. § 203. DHS’s customs enforcement responsibilities, carried out
by CBP, derive from the U.S. Customs Service of the Department of Treasury. Id. § 203(1). DHS’s immigration
enforcement functions, which are carried out by CBP and a separate component, U.S. Immigration and Customs
Enforcement, derive from the former INS. Id. § 251.
33 19 U.S.C. § 1709(b).
34 See id. (“The term ‘officer of the customs’ means any officer of the Customs Service or any commissioned, warrant,
or petty officer of the Coast Guard, or agent or other person authorized by law or by the Secretary of the Treasury, or
appointed in writing by a collector, to perform the duties of an officer of the Customs Service.”); 19 C.F.R. § 101.1
(“The terms ‘Customs’ or ‘U.S. Customs Service’ mean U.S. Customs and Border Protection.”).
35 19 U.S.C. § 1496; see also id. § 1583(a)(1) (authorizing the warrantless search of international mail).
36 Id. § 1467; see also id. § 1499 (providing that imported merchandise subject to inspection generally shall remain in
“customs custody” until it has been inspected and is found to have been “truly and correctly invoiced and found to
comply with the requirements of the laws of the United States”).
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baggage, and merchandise arriving in the Customs territory of the United States from places
outside thereof are liable to inspection and search by a Customs officer.”37
Title 19 also authorizes the boarding of vehicles and vessels.38 Under 19 U.S.C. § 1581, customs
officers may board “any vessel or vehicle at any place in the United States or within the customs
waters” to “examine the manifest and other documents and papers,” or to “examine, inspect, and
search the vessel or vehicle and every part thereof and any person, trunk, package, or cargo on
board.”39 The statute defines “customs waters” to include areas within 4 leagues (i.e., 12 nautical
miles) of the U.S. coast.40 The statute also authorizes customs officers to seize any vessel or
vehicle that is subject to forfeiture, fine, or penalty.41 The statute permits the boarding of vessels
found anywhere in the United States or within customs waters, even if the vessel is not believed
to be coming from a foreign port.42
19 U.S.C. § 482 permits customs officers who have authority to board vessels to search “any
vehicle, beast, or person” suspected of carrying merchandise that is subject to customs duties or
that has been brought into the United States “in any manner contrary to law.”43 The statute
authorizes the officers to “search any trunk or envelope” for which there is “reasonable cause to
suspect there is merchandise which was imported contrary to law.”44

37 19 C.F.R. § 162.6; see also id. § 101.1 (“‘Customs territory of the United States’ includes only the States, the District
of Columbia, and Puerto Rico.”).
38 See 19 U.S.C. § 1401(a) (“The word ‘vessel’ includes every description of water craft or other contrivance used, or
capable of being used, as a means of transportation in water, but does not include aircraft.”), (j) (“The word ‘vehicle’
includes every description of carriage or other contrivance used, or capable of being used, as a means of transportation
on land, but does not include aircraft.”); United States v. Gonzalez, 688 F. Supp. 658, 664 (D.D.C. 1988) (“In 1935,
Congress passed the Anti-Smuggling Act (‘Act’), which significantly amended many of the Customs Service laws to
expand the agency’s jurisdiction to board vessels in international waters.”).
39 19 U.S.C. § 1581(a).
40 See id. §§ 1401(j), 1709(c) (“The term ‘customs waters’ means, in the case of a foreign vessel subject to a treaty or
other arrangement between a foreign government and the United States enabling or permitting the authorities of the
United States to board, examine, search, seize, or otherwise to enforce upon such vessel upon the high seas the laws of
the United States, the waters within such distance of the coast of the United States as the said authorities are or may be
so enabled or permitted by such treaty or arrangement and, in the case of every other vessel, the waters within four
leagues of the coast of the United States.”).
41 Id. § 1581(e); see also id. § 1595(a)(1) (providing that, if the customs officer has probable cause that any of the
merchandise or property is in a “dwelling house, store, or other building place,” he or she may seek a judicial warrant
authorizing entry into the house (during daytime only) or store or other building to search for and seize the
merchandise).
42 Federal regulations similarly provide that customs officers may board a vessel anywhere in the United States or
within “customs waters”; an American vessel on the high seas; or a vessel within a “customs-enforcement area” (an
area on the high seas adjacent to customs waters where a vessel is being kept to prevent the unlawful importation of
persons or merchandise) to inspect the vessel and review documentation. 19 C.F.R. § 162.3(a); 19 U.S.C. § 1701(a).
But “Customs officers shall not board a foreign vessel upon the high seas in contravention of any treaty with a foreign
government, or in the absence of a special arrangement with the foreign government concerned.” 19 C.F.R. § 162.3(a).
See also id. § 162.5 (“A customs officer may stop any vehicle and board any aircraft arriving in the United States from
a foreign country for the purpose of examining the manifest and other documents and papers and examining,
inspecting, and searching the vehicle or aircraft.”).
43 19 U.S.C. § 482(a); see also 19 C.F.R. § 162.7 (“A Customs officer may stop, search, and examine any vehicle,
person, or beast, or search any trunk or envelope wherever found, in accordance with section 3061 of the Revised
Statutes (19 U.S.C. 482).”).
44 19 U.S.C. § 482(a). The Supreme Court has held that the statute permits customs officers to inspect incoming
international mail if there is “reasonable cause” that it contains unlawfully imported merchandise. United States v.
Ramsey, 431 U.S. 606, 611–12 (1977). The Court described the statute’s “reasonable cause” standard as being “less
stringent” that than the probable cause standard that generally applies to government searches under the Fourth
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Additionally, under 19 U.S.C. § 1589a, customs officers may make warrantless arrests for any
criminal offense under federal law that is committed in the officers’ presence; or for any felony
under federal law that is committed outside the officers’ presence if the officers have reasonable
grounds to believe the suspect has committed the felony.45
Coast Guard Authority
Title 14 of the U.S. Code sets forth powers exclusive to the Coast Guard.46 Under 14 U.S.C. §
522, Coast Guard officers may stop and board any vessel on “the high seas and waters over which
the United States has jurisdiction,” so long as the vessel is “subject to the jurisdiction, or to the
operation of any law, of the United States.”47 Unlike 19 U.S.C. § 1581, the statute’s reach extends
beyond the United States’ customs waters to the “high seas,” defined as “all parts of the sea that
are not included in the territorial sea or in the internal waters of any nation.”48 Under the statute,
Coast Guard officers may question a vessel’s occupants, examine documentation, and conduct
inspections and searches of the vessel to investigate potential violations of federal law.49 The
statute also permits officers to arrest for violations of federal law (including arresting an
individual escaping from the vessel to shore), and to seize any vessel or merchandise involved in
criminal activity.50
A table comparing federal statutes authorizing warrantless searches by customs officers generally,
and those pertaining to the search and boarding authority specific to the Coast Guard, can be
found in the Appendix at Table A-1.
Federal Immigration Laws and Regulations
DHS is the federal agency primarily charged with the administration and enforcement of
immigration laws.51 Within DHS, CBP is the agency component mainly responsible for
immigration enforcement along the border and at designated ports of entry52 and typically

Amendment. Id. at 612 ̶ 13.
45 19 U.S.C. § 1589a(3).
46 See 14 U.S.C. Subpt. I, Ch. 5. The Coast Guard also has authority to enforce customs laws under Title 19 of the U.S.
Code (discussed above). 19 U.S.C. § 1709(b). Previously part of the Department of Transportation, the Coast Guard is
now an entity housed within DHS. See 6 U.S.C. § 468(b). During wartime, the Coast Guard can be transferred to the
Department of Navy upon direction from either Congress or the President. 14 U.S.C. § 103(b). This section, however,
only discusses the statutory authorities applicable to the Coast Guard in its role in maritime law enforcement, and does
not address other authorities that might be applicable in a wartime context.
47 Id. § 522(a). The phrase “subject to the jurisdiction, or to the operation of any law, of the United States” does not
cover only American flag vessels. United States v. Williams, 617 F.2d 1063, 1076 (5th Cir. 1980). It also covers
foreign vessels on the high seas that are engaged in criminal offenses that have an effect on U.S. sovereign territory
(e.g., a conspiracy to violate federal narcotics laws). Id. (citing United States v. Cadena, 585 F.2d 1252, 1257 (5th Cir.
1978)).
48 33 U.S.C. § 1601. The “territorial sea” of the United States is defined as the area within 12 nautical miles of the U.S.
coastline (i.e., the customs waters). Id. § 3507.
49 14 U.S.C. § 522(a).
50 Id.; see also 46 U.S.C. § 70503(a) (prohibiting the manufacture or distribution of, or the possession with intent to
manufacture or distribute, a controlled substance on board a vessel).
51 See Homeland Security Act of 2002, Pub. L. No. 107-296, § 101(a), 116 Stat. 2135 (2002) (codified at 6 U.S.C.
§ 111(a)). As discussed in this report, DHS’s immigration enforcement functions derive from the former INS. 6 U.S.C.
§ 251.
52 See id. § 211(c) (listing functions of CBP).
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conducts immigration inspections and arrests in border regions.53 U.S. Immigration and Customs
Enforcement (ICE)—the DHS component tasked with interior enforcement and removal—may
also cooperate with CBP, such as in investigating cross-border criminal activity (e.g., human
trafficking, gang activity, drug smuggling).54
The Immigration and Nationality Act (INA)55 authorizes immigration officers to conduct searches
and seizures.56 This authority generally concerns the investigation of immigration violations, such
as the search of aliens suspected of unlawfully entering the country, but also generally permits the
arrest of persons (including U.S. citizens) who engage in certain criminal activity discovered
within the course of the officer’s duties.57
Under Section 287 of the INA, an immigration officer may conduct, under the terms of
regulations prescribed by the Secretary of DHS, several types of immigration enforcement actions
without a warrant,58 including at the border and surrounding areas.59 Under INA Section
287(a)(1), an immigration officer may, under the terms of prescribed regulations, “interrogate any
alien or person believed to be an alien as to his right to be or to remain in the United States.”60
DHS regulations similarly state that the officer may ask anyone questions so long as the officer
“does not restrain the freedom of an individual, not under arrest, to walk away.”61
INA Section 287(a)(3) provides that, “within a reasonable distance from any external boundary of
the United States,” an immigration officer may “board and search for aliens any vessel within the
territorial waters of the United States and any railway car, aircraft, conveyance, or vehicle” to
enforce federal immigration laws.62
DHS regulations define “external boundary” as “the land boundaries and the territorial sea of the
United States extending 12 nautical miles (i.e., roughly 13.8 land miles) from the baselines of the
United States determined in accordance with international law.”63
“Reasonable distance” is defined as “within 100 air miles (i.e., roughly 115 land miles) from any
external boundary of the United States” or “any shorter distance” set by the chief patrol agent of

53 Within CBP, the Office of Field Operations is the agency component that conducts inspections and enforces
immigration and customs laws at designated ports of entry. See id. § 211(g)(3). The U.S. Border Patrol is the CBP
component primarily charged with the apprehension of aliens unlawfully entering the United States or who have
recently entered the country unlawfully away from a designated point of entry; as well as the interdiction of goods that
are unlawfully imported into the United States. See id. § 211(e)(3).
54 See U.S. Immigr. & Customs Enf’t, Homeland Security Investigations (Jan. 8, 2020), http://www.ice.gov/about.
55 Immigration and Nationality Act of 1952, Pub. L. No. 82-414, 66 Stat. 163 (1952).
56 See id. § 287(a), (c) (codified at 8 U.S.C. § 1357(a), (c)); see also 8 C.F.R. §§ 287.1, 287.5 (implementing
regulations).
57 8 U.S.C. §§ 1225(a)(3), 1225(d)(1), 1357(a), (c).
58 Generally, an immigration officer must have an administrative “Warrant of Arrest” (Form I-200) to arrest and detain
an alien who is subject to removal from the United States. 8 U.S.C. § 1226(a); 8 C.F.R. § 236.1(b).
59 8 U.S.C. § 1357(a), (c); 8 C.F.R. §§ 287.1, 287.3, 287.5, 287.8.
60 8 U.S.C. § 1357(a)(1).
61 8 C.F.R. § 287.8(b)(1). But the officer may “briefly detain” an individual if he or she has reasonable suspicion that
the person being questioned is committing a crime or is unlawfully present in the United States. Id. § 287.8(b)(2).
62 8 U.S.C. § 1357(a)(3); see also id. § 1225(d)(1) (“Immigration officers are authorized to board and search any vessel,
aircraft, railway car, or other conveyance or vehicle in which they believe aliens are being brought into the United
States.”).
63 8 C.F.R. § 287.1(a)(1).
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CBP or special agent of ICE for a particular sector or district.64 Factors that may be considered
when setting a distance within this area include topography, confluence of arteries of
transportation leading from external boundaries, density of population, potential inconvenience to
the public, types of conveyances used, and reliable information about the movement of persons
who are unlawfully entering the United States.65 Additionally, the regulations provide the
possibility that, in “unusual circumstances,” a distance beyond 100 air miles from the border may
be deemed “reasonable.”66 For that to occur, the chief patrol agent or special agent must “forward
a complete report with respect to the matter to the Commissioner of CBP, or the Assistant
Secretary for ICE, as appropriate, who may, if he determines that such action is justified, declare
such distance to be reasonable.”67
Figure 1 shows a map of the area within 100 air miles of an external boundary of the United
States (shaded in pink), along with the factors considered by DHS in assessing whether a greater
or shorter distance may be set for particular sectors.

64 Id. § 287.1(a)(2). For boarding and searching aircraft, agency officials may set “any distance.” Id.
65 Id. § 287.1(b).
66 Id.
67 Id.
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Figure 1. Area Within 100 Air Miles of the U.S. Border

Factors Considered in Setting Distances Within 100-Air Mile Area*

Topography

Confluence of arteries of

Density of population
transportation leading from

Possible inconvenience to the traveling
external boundaries
public

Types of

Reliable information as to
* Unusual circumstances (may be considered in
conveyances
movements of persons effecting
setting distances greater than 100 air miles)
used
unlawful entry into the United
States
Source: Congressional Research Service; 8 C.F.R. § 287.1(a)(2), (b).
Note: This figure includes cities located within 100 miles of the country’s external boundary with a population
greater than 500,000 persons.
Although INA Section 287(a)(3) and implementing regulations give immigration officers broad
authority to conduct warrantless searches near the border, as will be discussed later in the report,
the Constitution sets limits on how this authority may be implemented.68 For that reason, the
government’s search authority along the border is not unfettered, and immigration officers’ ability
to conduct warrantless searches near the border are informed by a number of factors, including
population density and inconvenience to the public.69 Thus, the ability to conduct warrantless
searches in desolate border regions does not necessarily mean that such authority equally extends
to populated metropolitan areas near the border.70

68 See infra “Government Searches Beyond the Border and Its Functional Equivalent.”
69 8 C.F.R. § 287.1(b).
70 See Petition for Writ of Certiorari, Almeida-Sanchez v. United States, 413 U.S. 266 (1973) (No. 71-6278) (“Despite
the apparently unlimited authority the language of the statute seems to convey to board and search within a ‘reasonable
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Apart from authorizing searches near the border, INA Section 287(a)(3) authorizes certain
designated immigration officers “to have access to private lands” (but not dwellings) within 25
miles71 from any external boundary of the United States for the purpose of “patrolling the
border.”72 Under DHS regulations, “patrolling the border” means “conducting such activities as
are customary, or reasonable and necessary, to prevent the illegal entry of aliens into the United
States.”73 The U.S. Court of Appeals for the Ninth Circuit (Ninth Circuit)74 has held that INA
Section 287(a)(3)’s restriction on access to “dwellings” on private lands applies to homes,
including the residential curtilage (e.g., a backyard).75 The court reasoned that if “dwellings” was
narrowly interpreted to cover only a home’s physical structure, immigration officers would have
the “unchecked ability” to enter any private backyard near the border, so long as they did not
enter the physical structure itself.76 The court opined that it would be unreasonable to assume that
Congress intended to confer such “broad and sweeping powers” given the potential constitutional
issues raised by such a narrow construction of the statute.77
Under INA Section 287(a)(2), designated immigration officers may arrest an alien without a
warrant if (1) the alien is entering or trying to enter the United States unlawfully in the presence
or view of the officer; or (2) there is “reason to believe” the alien is unlawfully in the United

distance’ of the border, the statute has never been understood to permit arbitrary searches and has not been used as a
pretext to search for evidence of other criminal conduct. Thus, the establishment of checkpoints within the 100-mile
maximum fixed by regulation, 8 C.F.R. 287.1 (a)(2), is based upon a consideration of various factors designed to
accomplish the statutory objective with the least possible intrusion upon the privacy of travelers. Hence, as illustrated
by the present case, the INS has not claimed and would not claim statutory or constitutional authority to make random
vehicle inspections for aliens in Times Square or in front of the Lincoln Memorial, even though technically these points
are within 100 air miles of an external border. There is, quite simply, not a sufficient need for such operations to justify
the inconvenience they would cause, and thus they would be ‘unreasonable’ in the constitutional sense. But vehicle
checks conducted in areas where the incidence of illegal entry and alien smuggling is high are, if executed in good faith
and with minimum inconvenience to the traveling public, reasonable within the Fourth Amendment.”).
71 The statutory provision setting forth immigration officers’ ability to have access to private lands within a distance of
25 miles from an external U.S. boundary, 8 U.S.C. § 1357(a)(3), does not specify whether this measurement is in
statute miles (5,280 feet) typically used in land measurement or air/nautical miles (roughly 6,076.115 feet). Compare
Mile, Statute Mile, and Nautical Mile, BLACK’S LAW DICTIONARY (11th ed. 2019). The provision’s application to
searches arising on land would support construing “twenty-five miles” to mean 25 statute miles. Cf. Buttimer v. Detroit
Sulphite Transp. Co., 39 F. Supp. 222, 227 (E.D. Mich. 1941) (provision of Seamen’s Act concerning voyages of less
than “600 miles” meant nautical miles, because “it is presumed, unless otherwise specified, that distances on water
refer to nautical rather than land miles”). Related regulations concerning the powers and duties of immigration officers
do not provide further guidance, though two other terms used in the same statutory provision, relating to the “external
boundary” of the United States and a “reasonable distance” from that external boundary, are defined using air/nautical
mileage. 8 C.F.R. § 287.1(a)-(b).
72 8 U.S.C. § 1357(a)(3); 8 C.F.R. § 287.5(b). Under CBP policy, the officer must inform the owner or occupants of the
private lands that he or she intends to access those lands. See U.S. CUSTOMS & BORDER PROT., INSPECTOR’S FIELD
MANUAL § 18.6(d).
73 8 C.F.R. § 287.1(c).
74 This report references a number of decisions by federal appellate courts of various regional circuits. For purposes of
brevity, references to a particular circuit in the body of this report (e.g., the Ninth Circuit) refer to the U.S. Court of
Appeals for that particular circuit.
75 United States v. Romero-Bustamente, 337 F.3d 1104, 1110 (9th Cir. 2003).
76 Id. at 1109 (“Nonetheless, there are good reasons to eschew the plain meaning interpretation here, because it would
indeed work an absurd result. Excluding only dwellings, in the most restricted literal sense, from the Border Patrol’s
warrantless search authority would provide its agents the unchecked ability to enter every backyard in metropolitan San
Diego, Detroit, Buffalo, and El Paso, all of which are well within 25 miles of external borders of the United States.
Aside from the obvious constitutional implications of such an interpretation, we seriously doubt that Congress intended
to give the Border Patrol such unique and sweeping powers.”).
77 Id.
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States and likely to escape before a warrant can be obtained.78 INA Section 287(a) also permits
designated immigration officers to make warrantless arrests for criminal offenses in specified
circumstances (e.g., when the offense is committed in the officer’s presence, or there is “reason to
believe” the suspect committed a felony and would likely escape).79
INA Section 287(c) authorizes designated immigration officers to conduct a warrantless search of
a person who is seeking admission to the United States (and his or her personal belongings).80
There must be “reasonable cause” to suspect there are grounds for denying the person’s
admission that the search would disclose.81
A table listing INA provisions that authorize warrantless searches and seizures by immigration
officers can be found in Table A-2.
Border Searches and the Fourth Amendment
Although federal statute and implementing regulations provide designated government officers
with broad authority to conduct warrantless searches and seizures along or near international
borders for specified purposes, including to deter immigration and customs violations, there are
constitutional constraints to the exercise of this authority—the most notable being the Fourth
Amendment.82 This section provides a brief overview of Fourth Amendment concepts and then
examines how these concepts apply to searches and seizures conducted at or near the border.
Besides discussing the scope and reach of the border search exception, this section also briefly
identifies several other exceptions to generally applicable warrant requirements that may be
relevant to law enforcement encounters near the border.
General Overview of the Fourth Amendment
The Fourth Amendment protects against unreasonable searches and seizures by government
actors.83 It provides:
The right of the people to be secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but
upon probable cause… and particularly describing the place to be searched, and the persons
or things to be seized.84

78 8 U.S.C. § 1357(a)(2); 8 C.F.R. § 287.5(c)(1). Courts have viewed the “reason to believe” standard as equivalent to
probable cause. See Morales v. Chadbourne, 793 F.3d 208, 216 (1st Cir. 2015); United States v. Quintana, 623 F.3d
1237, 1239 (8th Cir. 2010); Tejeda-Mata v. INS, 626 F.2d 721, 725 (9th Cir. 1980); United States v. Cantu, 519 F.2d
494, 496 (7th Cir. 1975); Au Yi Lau v. INS, 445 F.2d 217, 222 (D.C. Cir. 1971).
79 8 U.S.C. § 1357(a)(4), (5); 8 C.F.R. § 287.5(c)(2)-(4).
80 8 U.S.C. § 1357(c); 8 C.F.R. § 287.5(d).
81 8 U.S.C. § 1357(c).
82 See, e.g., United States v. Brignoni-Ponce, 422 U.S. 873, 882–83 (1975) (statute giving immigration officers the
power to conduct warrantless searches within a “reasonable distance” of the border must be construed against the
backdrop of the Fourth Amendment); United States v. Nichols, 142 F.3d 857, 864–68 (5th Cir. 1998) (observing that
statutory authority of immigration officers to conduct searches within a “reasonable distance” of the border are subject
to the Fourth Amendment’s reasonableness requirements, and describing circuit case law as recognizing that searches
occurring more than 50 miles from the border are usually considered as being a “substantial distance” from the border)
(internal citation omitted).
83 U.S. CONST. amend. IV.
84 Id.
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The first portion of the Fourth Amendment, sometimes called the Reasonableness Clause,
enumerates what the amendment seeks to prohibit. It specifies that “the people” are protected;
that “persons, houses, papers, and effects” are covered; and the nature of the protection (“to be
secure . . . against unreasonable searches and seizures”). The second portion, sometimes called
the Warrant Clause, sets forth the requirements for a warrant to be issued, including “probable
cause” that a search will uncover evidence of wrongdoing.85
“The People” Protected by the Fourth Amendment
The Fourth Amendment secures the right of “the people” to be free from unreasonable searches
and seizures. At times, the Supreme Court has suggested that the category of individuals protected
by the Fourth Amendment is not coextensive with the category protected by the Fifth
Amendment, which applies to every “person” in the United States.86 In United States v. Verdugo-
Urquidez, the Supreme Court held that a foreign national arrested at his residence in Mexico and
involuntarily brought to the United States to stand trial did not come within the protective scope
of the Fourth Amendment.87 Writing for the Court, Chief Justice Rehnquist observed:
“[T]he people” seems to have been a term of art employed in select parts of the
Constitution. The Preamble declares that the Constitution is ordained and established by
“the People of the United States.” The Second Amendment protects “the right of the people
to keep and bear Arms,” and the Ninth and Tenth Amendments provide that certain rights
and powers are retained by and reserved to “the people.” See also U.S. CONST., Amdt. 1
(“Congress shall make no law . . . abridging . . . the right of the people peaceably to
assemble”) (emphasis added); Art. I, § 2, cl. 1 (“The House of Representatives shall be
composed of Members chosen every second Year by the People of the several States”)
(emphasis added). While this textual exegesis is by no means conclusive, it suggests that
“the people” protected by the Fourth Amendment, and by the First and Second
Amendments, and to whom rights and powers are reserved in the Ninth and Tenth
Amendments, refers to a class of persons who are part of a national community or who
have otherwise developed sufficient connection with this country to be considered part of
that community. . . .The language of these Amendments contrasts with the words “person”
and “accused” used in the Fifth and Sixth Amendments regulating procedure in criminal
cases.88

85 Id. See generally Illinois v. Gates, 462 U.S. 213, 231–38 (1983).
86 U.S. CONST. amend. V (providing that no “person” may be denied due process and other enumerated protections);
United States v. Verdugo-Urquidez, 494 U.S. 259, 265–66 (1990). See also Zadvydas v. Davis, 533 U.S. 678, 693
(2001) (“[T]he Due Process Clause applies to all “persons” within the United States, including aliens, whether their
presence here is lawful, unlawful, temporary, or permanent.”).
87 Verdugo-Urquidez, 494 U.S. at 274–75.
88 Id. at 265. Chief Justice Rehnquist’s opinion was joined by Justices Kennedy, O’Connor, Scalia, and Thomas. But
Justice Kennedy, who provided a critical vote to make the majority, also issued a concurring opinion indicating some
disagreement with the Chief Justice’s analysis. Id. at 275 (Kennedy, J.). While Justice Kennedy wrote that he “joined
the opinion of the Court” and believed “no violation of the Fourth Amendment occurred” in the present case, he
explained that he did not “place any weight on the reference to ‘the people’ in the Fourth Amendment as a source of
restricting its protections.” Id. at 275–276. Instead, Justice Kennedy believed the case turned primarily on the Fourth
Amendment’s extraterritorial application, which he characterized as a context-specific inquiry. Id at 277–78. This has
prompted some to describe Chief Justice Rehnquist’s opinion in Verdugo-Urquidez, at least with respect to its analysis
of “the people” protected by the Fourth Amendment, as reflecting the views of a plurality of the Court rather than a
five-Justice majority. See, e.g., The Hon. Karen Nelson Moore, Aliens and the Constitution, 88 N.Y.U. L. REV. 801,
808 (2013) (“[A] plurality led by Chief Justice Rehnquist declared that the expression ‘“the people” seems to have been
a term of art employed in select parts of the Constitution’ that extends certain rights to ‘a class of persons who are part
of a national community or who have otherwise developed sufficient connection with this country to be considered part
of that community.’ ”) (quoting Verdugo-Urquidez, 494 U.S. at 265). In any event, later courts have generally viewed
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In the years since Verdugo-Urquidez was decided, there appears to be little dispute that U.S.
citizens and lawfully present, resident aliens fall within the Fourth Amendment’s protective
scope.89 And in 2020, citing Verdugo-Urquidez and other cases, the Court declared that “it is long
settled as a matter of American constitutional law that foreign citizens outside U. S. territory do
not possess rights under the U. S. Constitution.”90 But there is less clarity regarding the Fourth
Amendment’s application to other categories of aliens, particularly those who are unlawfully
present in the United States.91
Some Supreme Court cases prior to Verdugo-Urquidez suggest that unlawfully present aliens are
among “the people” protected by the Fourth Amendment.92 For instance, Chief Justice
Rehnquist’s opinion in Verdugo-Urquidez acknowledged that in INS v. Lopez-Mendoza “a
majority of Justices assumed that the Fourth Amendment applied to illegal aliens in the United
States.”93 But the Chief Justice characterized that assumption as nonbinding dicta,94 and described
earlier Court decisions as “not dispositive on how the Court would rule on a Fourth Amendment
claim” brought by an unlawfully present alien.95
In the years since Verdugo-Urquidez, it appears that the majority of reviewing courts have held or
assumed that the Fourth Amendment applies to at least some unlawfully present aliens within the
United States.96 But some courts have concluded that some unlawfully present aliens do not

the framework set forth by the Chief Justice as controlling. See, e.g., United States v. Mesa-Rodriguez, 798 F.3d 664,
670 (2d Cir. 2015) (“At a minimum, Verdugo–Urquidez governs the applicability of the Fourth Amendment to
noncitizens. For Fourth Amendment rights to attach, the alien must show ‘substantial connections’ with the United
States.”); United States v. Portillo-Muñoz, 643 F.3d 437, 440 (5th Cir. 2011).
89 See, e.g., United States v. Barona, 56 F.3d 1087, 1094 (9th Cir. 1995) (reasoning that “the people” for purposes of
Fourth Amendment protection includes citizens at home and abroad and lawful resident aliens within U.S. borders, but
declining to decide on whether a resident alien is entitled to constitutional protections once he or she steps outside of
U.S. territory).
90 Agency for Int’l Dev. v. All. for Open Soc’y Int’l, Inc., 140 S. Ct. 2082, 2086 (2020).
91 Compare Perez Cruz v. Barr, 926 F.3d 1128, 1145 (9th Cir. 2019) (considering Fourth Amendment challenge to the
detention of an unlawfully present alien who had resided in the United States for many years); Martinez-Aguero v.
Gonzalez, 459 F.3d 618, 625 (5th Cir. 2006) (ruling that alien present within the United States had “developed
substantial connections” for purposes of bringing a Fourth Amendment challenge because she had regularly and
lawfully visited the country on prior occasions); with Castro v. Cabrera, 742 F.3d 595, 600–01 (5th Cir. 2014) (holding
that “excludable” aliens detained at the border could not bring a Fourth Amendment challenge to their detention by
immigration authorities); United States v. Gutierrez-Casada, 553 F. Supp. 2d 1259, 1272 (D. Kan. 2008) (“[T]he court
is examining the Fourth Amendment rights of a previously deported, aggravated felonious illegal alien who chose to
reenter the United States knowing that the sovereign country, by due process of law, had recently ordered him to leave
and stay out of the country. Simply put, such persons are not entitled to the same Fourth Amendment protections as are
ordinary citizens.”). See generally Moore, supra note 88, at 834–42 (discussing uncertainty regarding the Fourth
Amendment’s application to unlawfully present aliens in the years following Verdugo-Urquidez).
92 See Moore, supra note 88, at 834–35, 841–42 (discussing the relationship between Verdugo-Urquidez and other
cases where alienage did not appear to be a deciding factor in the Court’s Fourth Amendment analysis).
93 Verdugo-Urquidez, 494 U.S. at 272.
94 Id.
95 Id.
96 See, e.g., Perez Cruz, 926 F.3d at 1145 (holding that suspicionless detention of unlawfully present alien, who had
resided in the United States for more than a decade violated the Fourth Amendment); Yanez-Marquez v. Lynch, 789
F.3d 434, 445 (4th Cir. 2015) (considering Fourth Amendment claim raised by alien in removal proceedings); Cotzojay
v. Holder, 725 F.3d 172, 181 (2d Cir. 2013) (“[I]t is uncontroversial that the Fourth Amendment applies to aliens and
citizens alike.”); Martinez Carcamo v. Holder, 713 F.3d 916, 921 (8th Cir. 2013) (“We have observed that the Fourth
Amendment . . . applies as much to illegal aliens inside this country as it does to citizens.”); Martinez-Aguero, 459 F.3d
at 625 (observing in an excessive force case brought against a Border Patrol agent by a Mexican national with an
expired visa, and who had previously made monthly trips to the United States, that although “[t]here may be cases in
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receive protection under the Fourth Amendment because they lack the sufficient connections with
this country to be part of a “national community.”97 One district court, for example, rejected a
criminal defendant’s Fourth Amendment challenge to a search and seizure at the U.S.-Canada
border because, citing Verdugo-Urquidez, the defendant had not established a “significant
voluntary connection with the United States” to entitle him to Fourth Amendment protections.98
And some district courts, when applying Verdugo-Urquidez’s substantial connections test, have
held that previously deported felons are not entitled to Fourth Amendment protections because
their presence in the United States is prohibited by law.99
In short, whether aliens located within the interior of the United States who lack lawful
immigration status must satisfy the substantial connections test or a less stringent standard to
invoke Fourth Amendment protections remains unresolved by the courts.100 While many courts
have recognized that Fourth Amendment protections may apply to at least some unlawfully
present aliens, the circumstances of the aliens’ presence in the United States, including the nature
and length of their stay in the country, may be relevant.
There is some uncertainty regarding the application of the Fourth Amendment to nonresident
aliens seeking initial entry into the United States. Under Verdugo-Urquidez, such aliens arguably
lack Fourth Amendment protections because they lack substantial connections to the United
States. And courts have long held that aliens seeking to enter the United States have less robust
constitutional protections because they are deemed to be outside the country.101 But some courts

which an alien’s connection with the United States is so tenuous that he cannot reasonably expect the protection of its
constitutional guarantees; the nature and duration of [the Mexican national’s] contacts with the United States, however,
are sufficient to confer Fourth Amendment rights”); see also Moore, supra note 88, at 834–35 (“Given the prior
discussion of aliens’ Fifth and Sixth Amendment rights, it is perhaps not surprising that, generally speaking, aliens, just
as citizens, are entitled to the Fourth Amendment’s protections and to the exclusion, in domestic criminal proceedings,
of evidence obtained in violation of the Fourth Amendment. The Supreme Court implicitly endorsed this proposition in
1973 in Almeida-Sanchez v. United States, where the Court held that the warrantless search and seizure of a Mexican
citizen legally present in the United States violated the Fourth Amendment. In fact, the Almeida-Sanchez Court did not
even consider the impact of alienage on the analysis; instead, Justice Stewart, writing for the plurality, focused on
whether the search was properly encompassed within the administrative border-search exception.”).
97 See, e.g., United States v. Portillo-Muñoz, 643 F.3d 437, 440 (5th Cir. 2011) (“[N]either this court nor the Supreme
Court has held that the Fourth Amendment extends to a native and citizen of another nation who entered and remained
in the United States illegally.”); Gutierrez-Casada, 553 F. Supp. 2d at 1272 (holding that a previously deported
criminal alien who had unlawfully reentered the United States did not receive Fourth Amendment protections); United
States v. Esparza-Mendoza, 265 F. Supp. 2d 1254, 1271–73 (D. Utah 2003) (same); United States v. Ullah, No. 04-CR-
30A(F), 2005 WL 629487, at *30 (W.D.N.Y. Mar. 17, 2005) (“The record in the instant case, however, is devoid of
any evidence demonstrating that Ullah, an alien, had lawfully entered and resided in this country for a sufficient period
to trigger the application of Fourth or Fifth Amendment protections to the challenged border inspections to which he
was subjected.”).
98 Ullah, 2005 WL 629487, at *29.
99 Gutierrez-Casada, 553 F. Supp. 2d at 1272 (holding that, in light of Verdugo-Urquidez, a previously deported,
felonious, unlawfully present alien was not entitled to Fourth Amendment protections); Esparza-Mendoza, 265 F.
Supp. 2d at 1271 (holding that “previously deported alien felons, such as [defendant], are not covered by the Fourth
Amendment”).
100 See Mary Holper, The Unreasonable Seizures of Shadow Deportations, 86 U. CIN. L. REV. 923, 950 (2018) (“A
question that has gained increasing relevance since 1990, when the Court decided United States v. Verdugo-Urquidez,
is whether undocumented noncitizens are part of ‘the people’ protected by the Fourth Amendment.”); D. Carolina
Nuñez, Inside the Border, Outside the Law: Undocumented Immigrants and the Fourth Amendment, 85 S. CAL. L. REV.
85, 108 (2011) (noting that “there is no consensus on which classes of undocumented immigrants are outside the Fourth
Amendment’s ambit”).
101 See Zadvydas v. Davis, 533 U.S. 678, 693 (2001) (“It is well established that certain constitutional protections
available to persons inside the United States are unavailable to aliens outside of our geographic borders.”); Landon v.
Plasencia, 459 U.S. 21, 32 (1982) (“This Court has long held that an alien seeking initial admission to the United States
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have ruled that these constitutional limitations pertain only to challenges to procedures arising in
the context of immigration, and do not foreclose Fourth Amendment claims that implicate certain
fundamental rights, including when raised by nonresident aliens at the border.102
Searches
As discussed earlier, the Fourth Amendment protects against unreasonable searches and seizures.
Searches potentially affronting the Fourth Amendment tend to fall into two categories: (1)
searches of premises and other effects; and (2) searches of the person. A search of an area where
there is a reasonable expectation of privacy generally implicates the Fourth Amendment. Whether
a search has occurred is often determined by a two-part test set forth in Justice Harlan’s
concurring opinion to the Supreme Court’s decision in Katz v. United States: “first, that a person
have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be
one that society is prepared to recognize as ‘reasonable.’”103 A search may also occur on a
trespass theory, that is, where the government obtains information by physically intruding on a
constitutionally protected area, such as a home.104
The Fourth Amendment also protects against unreasonable searches of the person.105 The
Supreme Court has found that intrusions on the body—whether by, for example, an external pat

requests a privilege and has no constitutional rights regarding his application, for the power to admit or exclude aliens
is a sovereign prerogative.”); Shaughnessy v. United States ex rel. Mezei, 345 U.S. 206, 212 (1953) (declaring that “an
alien on the threshold of initial entry stands on a different footing” than those who have “passed through our gates” for
purposes of receiving due process protections); Alvarez-Garcia v. Ashcroft, 378 F.3d 1094, 1097 (9th Cir. 2004)
(“Aliens ‘standing on the threshold of entry’ are ‘not entitled to the constitutional protections provided to those within
the territorial jurisdiction of the United States.’ ”) (quoting Ma v. Ashcroft, 257 F.3d 1095, 1107 (9th Cir.2001)). Cf.
DHS v. Thuraissigiam, 140 S. Ct. 1959, 1982–83 (2020) (An alien arriving at a U.S. port of entry, whether at a land
border or an international airport, is a “treated for due process purposes as if stopped at the border” despite being on
U.S. soil; this principle also extends to the treatment of an alien apprehended 25 yards from the border following his
unlawful entry.).
102 See Castro v. Cabrera, 742 F.3d 595, 600 (5th Cir. 2014) (“Therefore, if these detainees are excludable aliens
stopped before entry into the United States and their claims arise in the context of immigration, the entry fiction applies
and there is no violation of the Fourth Amendment. If, however, they were subject to wanton or malicious infliction of
pain or gross physical abuse, the doctrine does not apply, and we consider whether Cabrera was entitled to qualified
immunity.”); Martinez-Aguero v. Gonzalez, 459 F.3d 618, 623 (5th Cir. 2006) (holding that alien detained near the
border could be considered within the United States for purposes of asserting a Fourth Amendment claim because she
sought to challenge an officer’s use of excessive force outside the context of her immigration detention); Kwai Fun
Wong v. INS, 373 F.3d 952, 971 (9th Cir. 2004) (“The entry fiction thus appears determinative of the procedural rights
of aliens with respect to their applications for admission. The entry doctrine has not, however, been applied, by the
Supreme Court or by this court, to deny all constitutional rights to non-admitted aliens.”) (emphasis in original);
Tungwarara v. United States, 400 F. Supp. 2d. 1213, 1220 (N.D. Cal. 2005) (holding that the Fourth Amendment
requires “some level of suspicion” to conduct strip searches of non-admitted aliens because “intrusive searches of the
person implicate important dignity and privacy interests,” and “[t]hese interests are fundamental to all human beings,
not just admitted aliens and citizens”) (citing United States v. Flores-Montano, 541 U.S. 149, 152 (2004)).
103 Katz v. United States, 389 U.S. 347, 361 (1967) (Harlan, J., concurring) (ruling that the bugging of a phone booth
violated Katz’s Fourth Amendment right to be free from unreasonable search).
104 United States v. Jones, 565 U.S. 400, 406–07 (2012) (holding that the attachment of a GPS tracking device to a
vehicle and tracking of the vehicle’s movements was a search under the Fourth Amendment).
105 U.S. CONST. amend. IV (providing that “[t]he right of the people to be secure in their persons . . . against
unreasonable searches and seizures . . . shall not be violated”).
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down of a person106 or a surgical procedure to remove a bullet allegedly stemming from an
attempted robbery107—constitute searches for purposes of the Fourth Amendment.108
Once a search subject to Fourth Amendment scrutiny has occurred, a determination must be made
on whether it is “reasonable.”109 Reasonableness depends on the context. The Court has explained
that “the reasonableness standard ‘is judged by balancing its intrusion on the individual’s Fourth
Amendment interests against its promotion of legitimate governmental interests.’”110
Seizures
The Fourth Amendment also protects against unreasonable seizures of persons or property by law
enforcement. A seizure of property subject to Fourth Amendment scrutiny occurs when
governmental action meaningfully interferes with the suspect’s possessory interests.111 Such items
are typically stolen property and other “fruits” of criminal conduct, instrumentalities used in
committing a crime, contraband, and items that may constitute evidence of the commission of a
crime or of someone’s guilt.112 In most cases there must be probable cause to effect a seizure.113
The Fourth Amendment guards against seizures of the person.114 A person has been seized if, in
view of all the circumstances surrounding the incident, that person has an objective reason to
believe that he or she is not free to leave.115 As the Supreme Court has explained, an arrest—“the
quintessential ‘seizure of a person’”116—“requires either physical force ... or, where that is
absent, submission to the assertion of authority.”117 The Court has also held that the use of
physical force to apprehend a person evading arrest (e.g., shooting a fleeing suspect) constitutes a
seizure, even if the person does not submit and is not subdued.118
Other forms of detention, such as field detentions for investigation, may also be subject to Fourth
Amendment scrutiny.119 Courts generally conclude that if an individual is approached by an

106 See, e.g., Terry v. Ohio, 392 U.S. 1, 25 (1968) (reasoning that a search incident to an arrest and a limited search for
weapons on the person can justify a “relatively extensive exploration of a person”).
107 Winston v. Lee, 470 U.S. 753 (1985).
108 See Schmerber v. California, 384 U.S. 757, 768 (1966).
109 Vernonia Sch. Dist. 47J v. Acton, 515 U.S. 646, 653 (1995).
110 Id. at 652–53.
111 United States v. Jacobsen, 466 U.S. 109, 113 (1984).
112 Warden, Md. Penitentiary v. Hayden, 387 U.S. 294 (1967) (ruling that the Fourth Amendment permitted the seizure
of evidence “which would aid in apprehending and convicting criminals”); see also FED. R. CRIM. P. 41(c) (authorizing
issuance of a warrant to seize “evidence of a crime”; “contraband, fruits of crime, or other items illegally possessed”;
“property designed for use, intended for use, or used in committing a crime”; or “a person to be arrested or a person
who is unlawfully restrained”).
113 See Arizona v. Hicks, 480 U.S. 321, 326–27 (1987) (holding seizure in plain view must be supported by probable
cause).
114 U.S. CONST. amend. IV.
115 Michigan v. Chesternut, 486 U.S. 567, 573 (1988); see also United States v. Mendenhall, 446 U.S. 544, 553–54
(1980) (“We adhere to the view that a person is ‘seized’ only when, by means of physical force or a show of authority,
his freedom of movement is restrained.”).
116 California v. Hodari D., 499 U.S. 621, 624 (1991).
117 Id. at 626 (rejecting argument that an arrest “effected by the slightest application of physical force, despite the
arrestee’s escape” constitutes a seizure).
118 Torres v. Madrid, -- S. Ct. --, No. 19-292, 2021 WL 1132514, *7 (Mar. 25, 2021). See also Tennessee v. Garner,
471 U.S. 1, 7 (1985).
119 See, e.g., Terry v. Ohio, 392 U.S. 1, 4–6 (1968). In the seminal stop-and-frisk case, Terry v. Ohio, an officer
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officer and asked questions without the use of force, the individual is only “seized” if a
reasonable person would not feel free to disregard the police and walk away.120 An example of a
common “seizure” is the stopping of an automobile and its passengers, even if the stop is brief
and limited in scope.121
Once there has been a “seizure,” the Fourth Amendment requires an appraisal of whether that
seizure was a reasonable “invasion of a citizen’s personal security.”122
Standards of Suspicion: Probable Cause and Reasonable Suspicion
Typically, a government officer must have probable cause before he or she may make an arrest,
conduct a search, or obtain a warrant.123 The probable cause standard stems from the Fourth
Amendment’s requirement that “no Warrants shall issue, but upon probable cause.”124 This
requirement “protects citizens from rash and unreasonable interferences with privacy and from
unfounded charges of crime, while giving fair leeway for enforcing the law in the community’s
protection.”125 The Supreme Court has recognized that probable cause is a concept that is
imprecise, fluid, and dependent on the context of the search or seizure.126 Generally, there must be
an objectively reasonable basis for believing (1) a crime was committed (for an arrest)127 or (2)
evidence of the crime is present in the place to be searched (for a search).128 Mere suspicion is not
enough to satisfy this standard, but probable cause requires less than evidence which would
justify a conviction.129

observed that multiple persons were “hover[ing] about a street corner for an extended period of time,” were not waiting
for anyone or anything to happen, paced along an identical route, and regularly conferred. Id. Suspecting the
individuals of criminal activity, the officer approached the individuals to investigate. Id. at 7. The Court held that a
brief investigatory stop and search constituted a seizure and search subject to the reasonableness requirement of the
Fourth Amendment, even though the brief detention fell short of an arrest. Id. at 16.
120 Mendenhall, 446 U.S. at 553–54.
121 Delaware v. Prouse, 440 U.S. 648, 654 (1979) (explaining that the “permissibility of a particular law-enforcement
practice is judged by balancing its intrusion on the individual’s Fourth Amendment interests against its promotion of
legitimate governmental interests”); see also Mich. Dep’t. of State Police v. Sitz, 496 U.S. 444, 450 (1990) (holding
that a seizure subject to the constraints of the Fourth Amendment occurs when a vehicle is stopped at a temporary
sobriety checkpoint conducted by police).
122 Terry, 392 U.S. at 19.
123 See, e.g., Kentucky v. King, 563 U.S. 452, 459 (2011) (“[A] warrant may not be issued unless probable cause is
properly established[.]”); Brigham City, Utah v. Stuart, 547 U.S. 398, 402 (2006) (explaining exigent circumstance
search exception to the warrant requirement requires probable cause); Maryland v. Pringle, 540 U.S. 366, 370 (2003)
(requiring probable cause for warrantless arrest in a public place for a felony).
124 U.S. CONST. amend. IV (emphasis added).
125 Pringle, 540 U.S. at 370 (quoting Brinegar v. United States, 338 U.S. 160, 176 (1949)) (internal quotation marks
omitted)).
126 See Illinois v. Gates, 462 U.S. 213, 232 (1983) (“Perhaps the central teaching of our decisions bearing on the
probable cause standard is that it is a ‘practical, nontechnical conception.’ Brinegar v. United States, 338 U.S. 160
(1949) . . . [P]robable cause is a fluid concept—turning on the assessment of the probabilities in particular factual
contexts—not readily, or even usefully, reduced to a neat set of legal rules.”).
127 Pringle, 540 U.S. at 371 (“To determine whether an officer had probable cause for an arrest, the court examines the
events leading up to the arrest, and then decides whether these historical facts, viewed from the standpoint of an
objectively reasonable police officer, amount to probable cause.”).
128 See Gates, 462 U.S. at 230–31 (applying totality of circumstances approach).
129 Dunaway v. New York, 442 U.S. 200, 212 (1979); Wong Sun v. United States, 371 U.S. 471, 479 (1963) (citation
omitted) (“It is basic that an arrest with or without a warrant must stand upon firmer ground than mere suspicion,
though the arresting officer need not have in hand evidence which would suffice to convict.”).
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Although probable cause is generally required, some warrantless searches and seizures may be
based on “reasonable suspicion”—a less demanding standard—depending on the “totality of the
circumstances” surrounding the search or seizure.130 For instance, Fourth Amendment
jurisprudence allows for brief investigative stops when a law enforcement officer has “a
particularized and objective basis for suspecting the particular person of criminal activity.”131
Although a mere “hunch” does not create reasonable suspicion,132 the level of suspicion the
standard requires is “considerably less than proof of wrongdoing by a preponderance of the
evidence,” and “obviously less” than is necessary for probable cause.”133
Warrantless Searches and Seizures
To satisfy the Fourth Amendment’s reasonableness requirement, searches and seizures typically
require a government official to obtain a warrant based on probable cause.134 Searches and
seizures conducted without a warrant are presumptively unreasonable.135 But there are situations
in which a warrantless search may be reasonable under the Fourth Amendment including, as
discussed below, searches at international borders.
Searches at International Borders
Fourth Amendment jurisprudence recognizes searches and seizures at international borders as
exceptional cases for Fourth Amendment purposes.136 Under what is known as the border search
exception, searches performed at international borders do not generally require a warrant,
probable cause, or reasonable suspicion.137 This exception to the warrant and probable cause
requirements applies to outgoing as well as incoming travelers.138 The Supreme Court has stated
that searches at the border “are reasonable simply by virtue of the fact that they occur at the
border.”139 Citing a lower expectation of privacy at the border, the Court has articulated that “[t]he
Fourth Amendment balance between the interests of the Government and the privacy right of the

130 See Alabama v. White, 496 U.S. 325, 330–31 (1990).
131 Naverette v. California, 572 U.S. 393, 396 (2014).
132 Terry v. Ohio, 392 U.S. 1, 27 (1968).
133 Navarrete, 572 U.S. at 397 (quoting United States v. Sokolow, 490 U.S. 1, 7 (1989)).
134 See, e.g., Skinner v. Railway Labor Execs.’ Ass’n., 489 U.S. 602, 621–22 (1989).
135 See Horton v. California, 496 U.S. 128, 133 (1990). “Where a search is undertaken by law enforcement officials to
discover evidence of criminal wrongdoing, [the Supreme] Court has said that reasonableness generally requires the
obtaining of a judicial warrant.” Veronia Sch. Dist. 47J v. Acton, 515 U.S. 646, 653 (1995).
136 United States v. Ramsey, 431 U.S. 606, 617–19 (1977).
137 Id.
138 See United States v. Seljan, 547 F.3d 993, 999 (9th Cir. 2008) (noting that “searches at the international border of
both inbound and outbound persons or property” are subject to the border search doctrine); United States v. Odutayo,
406 F.3d 386, 392 (5th Cir. 2005) (“[W]e join our sister circuits in holding that the border search exception applies for
all outgoing searches at the border.”); United States v. Boumelhem, 339 F.3d 414, 420 (6th Cir. 2003)
(“Notwithstanding Boumelhem’s arguments, the border search exception applies to the search of the outgoing cargo
container here.”); United States v. Oriakhi, 57 F.3d 1290, 1297 (4th Cir. 1995) (“[W]e join the several other circuit
courts which have held that the Ramsey border search exception extends to all routine searches at the nation’s borders,
irrespective of whether persons or effects are entering or exiting from the country.”); United States v. Ezeiruaku, 936
F.2d 136, 143 (3d Cir. 1991) (holding that “the traditional rationale for the border search exception applies as well in
the outgoing border search context.”); see also D.E. v. Doe I, 834 F.3d 723, 727 (6th Cir. 2016) (border search of
motorist’s vehicle was lawful under the border search exception, even though the motorist claimed to have arrived at
the international border inadvertently and intended to turn around).
139 Ramsey, 431 U.S. at 616.
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individual is also struck much more favorably to the Government at the border.”140 That said, not
all searches at the border are per se reasonable under the Fourth Amendment. Some border
searches conducted in a particularly offensive manner—such as a body cavity search—may still
be limited by the Fourth Amendment.141 Simply stated, the reasonableness of a border search
depends on the circumstances of the search itself.142
The border search exception does not necessarily apply to each and every encounter between law
enforcement and persons at or near an international border. For example, as will be discussed
later, courts have held that “roving patrol” stops of vehicles near the border to question the
vehicle’s occupants must be justified by reasonable suspicion of unlawful activity.143 Rather, the
border search exception applies to searches occurring in the context of a border crossing, such as
when an individual arrives at a U.S. port of entry.
The Border and Its Functional Equivalent
Searches may potentially take place along any segment of the United States’ international border.
Government officials may perform searches at or near the land borders shared with Mexico and
Canada.144 Stops and searches may also be conducted at the “functional equivalent” of the
border.145 Because people can enter the country at points other than along the border, courts have
concluded that stops and searches conducted at the first point at which an entrant may practically
be detained to be the functional equivalent of the border.146 This includes an airport where an
international flight lands147 or the port where a ship docks after traveling from a foreign port.148
For instance, lower courts have determined that a pat-down of a passenger on a jetway departing
on an international flight took place at the functional equivalent of the border149 and the search of
a passenger arriving from a nonstop international flight at the Chicago O’Hare airport occurred at

140 United States v. Montoya de Hernandez, 473 U.S. 531, 539–40 n.4 (1985).
141 See id; see also United States v. Irving, 452 F.3d 110, 123 (2d Cir. 2006) (explaining that reasonable suspicion
would be required for a more invasive search); United States v. Whitted, 541 F.3d 480, 485–86 (3d Cir. 2008)
(contrasting “routine” “patdowns, frisks, luggage searches, and automobile searches” with “nonroutine” “body cavity
searches, strip searches, and x-ray examinations” that require reasonable suspicion).
142 See Montoya de Hernandez, 473 U.S. at 538 (noting that the Fourth Amendment’s balance of reasonableness is
qualitatively different at the international border than in the interior).
143 See, e.g., United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975) (requiring reasonable suspicion for roving
patrol stops near the border)
144 See, e.g., United States v. Chase, 503 F.2d 571 (9th Cir. 1974) (Mexico); United States v. Mastberg, 503 F.2d 465
(9th Cir. 1974) (Canada).
145 Almeida-Sanchez v. United States, 413 U.S. 266, 272–73 (1973).
146 See, e.g., United States v. Cardenas, 9 F.3d 1139, 1147 (5th Cir. 1993); United States v. Beras, 183 F.3d 22, 26 (1st
Cir. 1999). See also United States v. Bareno–Burgos, 739 F. Supp. 772, 778 (E.D.N.Y. 1990) (“Case law reflects that
the functional equivalent of the border need bear no particular time or space relationship to the actual border.”).
147 See, e.g., United States v. Yang, 286 F.3d 940, 944 (7th Cir. 2002) (explaining “even though Chicago is not an
international border, searches at customs at O’Hare are permissible under the functional equivalent doctrine.”); Beras,
183 F.3d at 26; United States v. Johnson, 991 F.2d 1287, 1290 (7th Cir. 1993) (search of passenger arriving on nonstop
international at O’Hare International Airport was at the functional equivalent to an international border). In other
words, passengers and cargo arriving on an international flight may be subject to an inspection, but passengers arriving
on a domestic flight are not subject to an inspection.
148 See, e.g., United States v. Prince, 491 F.2d 655 (5th Cir. 1974); United States v. LaFroscia, 485 F.2d 457 (2d Cir.
1973); Cardenas, 9 F.3d at 1147; United States v. Victoria-Peguero, 920 F.2d 77, 80 (1st Cir. 1990) (explaining that a
warrantless search at the functional equivalent of the sea border was consistent with Fourth Amendment).
149 Beras, 183 F.3d at 26.
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the functional equivalent.150 Additionally, post offices receiving international airmail are the
functional equivalent of the border.151 Importantly, these locations are treated as the functional
equivalent of the border only to the extent that a search at that location pertains to persons or
items believed to be traveling to or from the United States.152
Searches and Seizures: Routine and Nonroutine
Under the border search exception, federal officers may generally conduct warrantless searches of
persons and things upon their entry into the United States, without needing reasonable suspicion
or probable cause of wrongdoing.153 But, depending on the level of intrusion, some searches
performed at the international border may require reasonable suspicion.154 When determining
whether a search is reasonable, Fourth Amendment jurisprudence generally categorizes searches
at the border into two categories: routine searches and nonroutine searches—with the latter
requiring a level of particularized suspicion of illegal activity.
Routine Searches and Seizures
The Supreme Court has discussed what constitutes a nonroutine search;155 it has not explicitly
defined the scope of searches that may be categorized as routine. According to lower courts,
routine searches generally include searches of automobiles, baggage, and other goods entering the
country.156 Additionally, an individual seeking to enter the country may be required to submit to a
search of his or her outer clothing,157 which may include an examination of the contents of a
purse, wallet, or pockets and a canine sniff.158 While this is ongoing, the individual may be
subject to a brief detention.159

150 Johnson, 991 F.2d at 1290.
151 United States v. Ramsey, 431 U.S. 606, 620 (1977) (rejecting any distinction between items mailed to the United
States and items carried into the United States).
152 See, e.g., United States v. Jackson, 825 F.2d 853, 876 (5th Cir. 1987) (en banc). In that case, the Fifth Circuit held
that a highway checkpoint 14 miles from the international border did not constitute the functional equivalent of the
border because it did not contain traffic “‘international’ in character.” Id. The court explained that the equivalent of the
border must not “intercept no more than a negligible number of domestic travelers.” Id. at 860.
153 See United States v. Montoya de Hernandez, 473 U.S. 531, 538 (1985); United States v. Lincoln, 494 F.2d 833, 837
(9th Cir. 1974); United States v. King, 485 F.2d 353, 358 (10th Cir. 1973); United States v. Beck, 483 F.2d 203, 207
(3d Cir. 1973); United States v. Stornini, 443 F.2d 833, 835 (1st Cir. 1971).
154 See Montoya de Hernandez, 473 U.S. at 537–38 (discussing Fourth amendment reasonableness requirement at the
border).
155 See generally id.
156 See, e.g., Angulo v. Brown, 978 F.3d 942, 949 (5th Cir. 2020) (“The Government does not need to show any level
of suspicion to thoroughly search an entrant’s vehicle at the border.”); United States v. Sandoval Vargas, 854 F.2d 1132
(9th Cir. 1988) (car); United States v. Flores, 594 F.2d 438 (5th Cir. 1979) (car); United States v. Lafroscia, 485 F.2d
457 (2d Cir. 1973) (car); United States v. Gonzalez, 483 F.2d 223 (2d Cir. 1973) (baggage); United States v. Stornini,
443 F.2d 833 (1st Cir. 1971) (baggage).
157 See, e.g., United States v. Braks, 842 F.2d 509 (1st Cir. 1988) (holding that requiring a female suspect to lift her
dress somewhat in a private room with a female inspector present was part of routine border search); United States v.
Nieves, 609 F.2d 642 (2d Cir. 1979) (holding that requiring a person to remove a shoe is part of routine border search
but drilling into shoes is not routine border search); United States v. Flores, 477 F.2d 608 (1st Cir. 1973).
158 See, e.g., United States v. Kelly, 302 F.3d 291, 294–95 (5th Cir. 2002) (canine sniff was routine border search,
reasoning a canine sniff “is no more intrusive than a frisk or a pat-down, both of which clearly qualify as routine border
searches”).
159 See, e.g., Angulo, 978 F.3d at 950 (ruling that an hour of questioning was within the government’s power and that
“removing Angulo from his vehicle and handcuffing him were only necessary because Angulo refused to exit the
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As explained by the Seventh Circuit, a routine search is one that does “not pose a serious invasion
of privacy” and “embarrass or offend the average traveler.”160 For instance, the removal and
examination of a suitcase’s contents, including through the use of an x-ray, by a customs
inspector constitutes a routine search.161 Similarly, the Fifth Circuit has defined a “routine” search
as “one that does not ‘seriously invade a traveler’s privacy,’” thereby requiring a reviewing court
to evaluate “‘the invasion of the privacy and dignity of the individual.’”162 The Fifth Circuit has
classified “ordinary pat-downs or frisks, removal of outer garments or shoes, and emptying of
pockets, wallets, or purses” as routine.163 Likewise, the Second Circuit has described routine
searches as to include searches of outer clothing, luggage, a purse, wallet, pockets, or shoes,
“which, unlike strip searches, do not substantially infringe on a traveler’s privacy rights.”164
In United States v. Braks, the First Circuit set forth several factors relevant to assessing whether a
search was routine.165 In that case, a customs official had searched a foreign national by taking
her into a private room and conducting a search of her garments by gesturing without physical
contact, resulting in the foreign national raising her garment.166 In determining the degree of
invasiveness of any particular search, the First Circuit set forth several factors to consider:
(i) whether the search results in the exposure of intimate body parts or requires the suspect
to disrobe; (ii) whether physical contact between Customs officials and the suspect occurs
during the search; (iii) whether force is used to effect the search; (iv) whether the type of
search exposes the suspect to pain or danger; (v) the overall manner in which the search is
conducted; and (vi) whether the suspect’s reasonable expectations of privacy, if any, are
abrogated by the search.167
The court concluded that the search was a justified and routine search on the rationale that the
foreign national did not have to actually remove her clothing or expose herself; no physical
contact or force was used; the search did not include any pain or danger; and the search was
conducted in a private room by a female customs official.168 The First Circuit explained that this
list of factors is not exhaustive, stressing that “each case must turn upon its particularized
facts.”169

vehicle voluntarily on his own”); United States v. Nava, 363 F.3d 942 (9th Cir. 2004) (individual was not subject to an
“arrest” when officer asked him to exit truck, handcuffed him, escorted him to security office to be patted down, and
was required to wait while officer inspected pickup truck).
160 United States v. Johnson, 991 F.2d 1287, 1291 (7th Cir. 1993) (conducting a “scratch test,” “flex test,” and “weight
test” on baggage).
161 Id. at 1293–94 (during routine inspection, customs official developed reasonable suspicion that she was smuggling
contraband into the country).
162 Kelly, 302 F.3d at 294 (quoting United States v. Cardenas, 9 F.3d 1139, 1148 n.3 (5th Cir 1993); United States v.
Sandler, 644 F.2d 1163, 1167 (5th Cir. 1981)).
163 Kelly, 302 F.3d at 294.
164 Tabbaa v. Chertoff, 509 F.3d 89, 98 (2d Cir. 2007).
165 See United States v. Braks, 842 F.2d 509, 511–12 (1st Cir. 1988).
166 Id. at 510–11.
167 Id. at 511–12.
168 Id. at 512–13.
169 Id. at 513.
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Nonroutine Searches and Seizures Requiring Reasonable Suspicion
A court may determine a nonroutine search has occurred once a search goes beyond a limited
intrusion. Nonroutine border searches—such as prolonged detentions, strip searches, body cavity
searches, or involuntary x-ray searches—require reasonable suspicion.170
Inspections of Persons. The 1985 Supreme Court decision United States v. Montoya de
Hernandez offers insight into what searches and detentions at the border may be classified as
nonroutine searches and therefore require reasonable suspicion.171 In that case, an airline traveler
arrived at the Los Angeles International Airport from Bogotá, Colombia.172 Upon questioning by
customs inspectors, the traveler revealed that she did not speak English, did not have family or
other connections in the United States, was planning to purchase goods for her husband’s store in
Bogotá, possessed $5,000 in cash, and had no hotel reservations.173 Based on this information, her
frequent traveling to the United States, and firm abdomen, the customs inspectors suspected she
was smuggling narcotics through her alimentary canal and detained her until her bowels passed—
taking around 16 hours.174 In a challenge to criminal convictions for unlawful possession and
importation of cocaine, the Supreme Court ruled that her detention did not violate the Fourth
Amendment because—even though it went beyond the scope of a routine customs inspection—it
was based on reasonable suspicion that she was smuggling contraband.175
This decision articulated a few important principles when it comes to the constitutionality of
prolonged detentions and nonroutine searches. Montoya de Hernandez seemingly mandates that
searches beyond a routine search and detention at the border must be supported by reasonable
suspicion.176 Furthermore, Montoya de Hernandez suggests that detentions, even extended delays
of 16 or more hours, may be constitutionally permissible if the detention “was reasonably related
in scope to the circumstances which justified it initially.”177 There, the Court held that the
detention lasting 16 or more hours was reasonable under the circumstances because the time of
detention corresponded to the time it took for the defendant’s bowels to pass and therefore was
“necessary to either verify or dispel the suspicion was not unreasonable.”178
There are no bright-line rules on when a routine search or detention transforms into nonroutine. In
another Supreme Court decision, United States v. Flores-Montano, the Supreme Court held that a
one-hour delay incident to a border search did not render the search nonroutine and therefore did
not require suspicion, reasoning that “delays of one to two hours at international borders are to be
expected.”179 The Fourth Amendment does not “shield[] entrants from inconvenience or delay at

170 United States v. Montoya de Hernandez, 473 U.S. 531, 541 n.4 (1985). See, e.g., United States v. Garcia-Garcia, 319
F.3d 726, 730 (5th Cir. 2003) (alert by drug sniffing dog constituted reasonably suspicion supporting detention of bus
for time reasonably necessary to investigate the cause of the alert).
171 473 U.S. 531 (1985).
172 Id. at 532–33.
173 Id. at 533.
174 Id. at 534.
175 Id. at 541.
176 See id. at 541–42.
177 Montoya de Hernandez, 473 U.S. at 542.
178 Id. at 544.
179 United States v. Flores-Montano, 541 U.S. 149, 155 n.3 (2004).
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the international border.”180 Rather, the focus is on whether the detention was reasonable in light
of the circumstances.181
A lower court’s opinion suggests that even searches and detentions lasting several hours may not
require reasonable suspicion. In Tabbaa v. Chertoff, the Second Circuit considered whether a
search and a detention lasting four to six hours at the U.S.-Canada border violated the plaintiffs’
Fourth Amendment rights.182 The U.S. citizen plaintiffs claimed the combined effect of the
measures used—intrusive questioning, photographing, and fingerprinting—was not routine and
therefore required some level of suspicion.183 The court held that the combined effect of routine
elements did not transform the stop into a nonroutine search because each of the individual
elements themselves were routine.184 The court also rejected the plaintiffs’ contention that the
threat of detention until they complied transformed the search into a nonroutine search, reasoning
that “border crossers cannot, by their own non-compliance, turn an otherwise routine search into a
nonroutine one.”185 Lastly, the Second Circuit held that the detention was routine because
“common sense and ordinary human experience suggest that it may take up to six hours for CBP
to complete the various steps at issue here, including vehicle searches, questioning, and identity
verification, all of which [were] already found to be routine.”186
Searches of Vehicles. As discussed previously, government officials may search automobiles
seeking entry to the United States without reasonable suspicion.187 But in United States v. Flores-
Montano, the Supreme Court considered whether a more intrusive search of a car—involving the
removal, disassembly, and reassembly of a fuel tank—constituted a search requiring suspicion of
illegal activity.188 Noting the government’s “paramount interest in protecting the border,” the
Court held that the government’s authority to conduct suspicionless border inspections includes
the authority to remove, disassemble, and reassemble a fuel tank.189 But the Flores-Montano court
declined to address whether and under what circumstances a search of a vehicle at the
international border would “be deemed unreasonable because of the particularly offensive manner
in which it is carried out.”190
Still, there is no hard-and-fast rule for when a search of a vehicle becomes so intrusive as to
require reasonable suspicion. Before Flores-Montano, several circuit courts held that the
government must have reasonable suspicion before drilling into an individual’s property in search

180 Id.
181 Montoya de Hernandez, 473 U.S. at 542.
182 Tabbaa v. Chertoff, 509 F.3d 89, 95 (2d Cir. 2007) (involving U.S. citizen plaintiffs who were returning from an
Islamic conference in Canada).
183 Id. at 98.
184 Id. at 99.
185 Id. at 100.
186 Id. (internal quotation marks omitted).
187 See Carroll v. United States, 267 U.S. 132, 154 (1925).
188 United States v. Flores-Montano, 541 U.S. 149, 151 (2004).
189 Id. at 155.
190 Id. at 155 n.2 (internal citation and quotation marks omitted).
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of contraband.191 The Supreme Court distinguished Flores-Montano from these circuit decisions
because the fuel tank was reassembled, unlike “potentially destructive drilling.”192
Several Ninth Circuit decisions post Flores-Montano support the notion that destruction to a
vehicle or its components might not require suspicion of illegal activity (other circuit courts have
not weighed in since Flores-Montano193). In United States v. Cortez-Rocha, the Ninth Circuit held
that cutting open a spare tire did not require reasonable suspicion.194 Although the court
acknowledged the damage to the tire, the court observed that the destruction of the spare tire did
not interfere with the operation of the vehicle or hinder the traveler’s immediate ability to
continue his travels using that automobile.195 In another decision, the Ninth Circuit held that the
drilling of a single small-diameter hole in a pickup truck did not require reasonable suspicion
because it did not significantly damage the truck.196 But in United States v. Guzman-Padilla, the
Ninth Circuit held that the deflating of tires required reasonable suspicion because the vehicle
was rendered inoperable.197 Guzman-Padilla clarified the factors for determining whether a
search of a vehicle required reasonable suspicion: “(1) Did the search damage the vehicle in a
manner that affected the vehicle’s safety or operability, and (2) Was the search conducted in a
particularly offensive manner.”198 In other words, damage to a vehicle does not transform a border
search into a nonroutine search; the severity of that damage to the vehicle’s functionality may be
a key consideration in assessing whether reasonable suspicion is required.
Other Exceptions to the Fourth Amendment’s Warrant Requirement
That May Be Relevant to Encounters Near the Border
In addition to the border search exception, courts have recognized other circumstances where a
warrantless search may be permitted under the Fourth Amendment. Some of these exceptions
may be relevant to law enforcement encounters at or near the international border or its functional
equivalent:
 Search Incident to Lawful Arrest. A government officer who lawfully arrests an
individual may conduct a warrantless search of the arrestee’s person and the area
“within his immediate control” from which the suspect might gain possession of

191 See, e.g., United States v. Rivas, 157 F.3d 365, 367 (5th Cir. 1998) (holding drilling into the body of a trailer
required reasonable suspicion); Untied States v. Robles, 45 F.3d 1 (1st Cir. 1995) (drilling into machine part required
reasonable suspicion); United States v. Carreon, 872 F.2d 1436 (10th Cir. 1989).
192 Flores-Montano, 541 U.S. at 155 n.2.
193 But see United States v. De Jesus-Viera, 655 F.3d 52 (1st Cir. 2011). In that case, the First Circuit held that a
drilling by CBP into a vehicle did not violate the Fourth Amendment. Id. at 58. The trial court had concluded that the
drilling was a routine border search. Id. at 57–58. But on appeal, the First Circuit declined to weigh in on whether the
search was a routine search or a nonroutine search because, even if it was nonroutine, there was reasonable suspicion to
justify the drilling. Id. at 58.
194 United States v. Cortez-Rocha, 394 F.3d 1115, 1119–20 (9th Cir. 2006) (concluding that the search and disabling of
a vehicle’s spare tire “does not in any way hinder the operation of the vehicle or impede the traveler’s immediate ability
to continue his travels using the vehicle”).
195 Id. at 1120.
196 United States v. Chaudhry, 424 F.3d 1051, 1053 (9th Cir. 2005).
197 United States v. Guzman-Padilla, 573 F.3d 865, 879 (9th Cir. 2009).
198 Id.; see also United States v. Hernandez, 424 F.3d 1056 (9th Cir. 2005) (holding no reasonable suspicion as required
where the government removed the interior door panels with a screwdriver so that doors could be put back together
without damage, causing no significant damage nor did it undermine the safety of the vehicle).
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a weapon or destructible evidence.199 This exception stems from interests in
officer safety and evidence preservation following an arrest.200
 Stop and Frisk. A law enforcement officer may detain an individual briefly upon
reasonable suspicion of criminal activity, and conduct a frisk when the officer is
“justified in believing that the individual . . . is armed and presently dangerous to
the officer or to others.”201 A frisk is limited to a search for weapons202 and
cannot be justified by a need to prevent the destruction of evidence (but in the
event a search for weapons leads to the discovery of contraband, that finding may
permit the officer to seize the item under the plain view exception discussed
below, and the discovery of contraband may lead to a criminal arrest).203 If a
search exceeds these bounds, it must be justified by a warrant or another
exception to the warrant requirement.204
 Emergency Aid, Exigent Circumstances, or Hot Pursuit. A warrantless search
may be permissible if the “exigencies of the situation make the needs of law
enforcement so compelling that a warrantless search is objectively reasonable
under the Fourth Amendment.”205 Examples of exigent circumstances include
providing emergency assistance in a residence or engaging in a “hot pursuit” of a
fleeing suspect.206
 Plain View. Government officers may seize an item of an incriminating nature in
“plain view” without a warrant.207 Examples of when such a seizure may be
permissible include when an officer comes across some other article of an
incriminating nature while performing a search of an area for certain objects
pursuant to a lawful warrant; when an officer finds an incriminating article while
the officer is engaged in a hot pursuit; or when an officer comes across an
incriminating object while conducting a search incident to a lawful arrest.208
 Searches in Open Fields. The Fourth Amendment does not protect against
searches in “open fields,” such as rural farmland, even if the intrusion onto the
lands is a common-law trespass.209 Open fields are distinct from a property

199 Davis v. United States, 564 U.S. 229, 232 (2011).
200 Arizona v. Gant, 556 U.S. 332, 338 (2009).
201 Adams v. Williams, 407 U.S. 143, 145 (1972) (citing Terry v. Ohio, 392 U.S. 1, 22 (1968)).
202 Terry, 392 U.S. at 29; see also Michigan v. Long, 463 U.S. 1032 (1983) (holding that protective search of a
vehicle’s passenger compartment during a lawful stop did not affront the Fourth Amendment where the circumstances
were such that a person would reasonably believe that his safety or the safety of others was at risk); Ybarra v. Illinois,
444 U.S. 85, 93–94 (1979) (“Nothing in Terry can be understood to allow a generalized ‘cursory search for weapons’
or indeed, any search whatever for anything but weapons.”); Adams, 407 U.S. at 146–47 (1972) (explaining a search of
weapons must be “limited in scope to this protective purpose”).
203 See Minnesota v. Dickerson, 508 U.S. 366, 374–75 (1993) (explaining that a search is no longer valid and its fruits
will be suppressed if a Terry protective search goes beyond what is necessary to determine whether the suspect is
armed).
204 See id. at 374–75.
205 Missouri v. McNeely, 569 U.S. 141, 148–49 (2013) (quoting Kentucky v. King, 563 U.S. 452, 460 (2011)).
206 Id. at 148–49.
207 Horton v. California, 496 U.S. 128, 134 (1990).
208 Coolidge v. New Hampshire, 403 U.S. 443, 465–66 (1971).
209 Hester v. United States, 265 U.S. 57, 58 (1924). An example of the open fields exception is found in Oliver v.
United States, 466 U.S. 170 (1984), in which police officers entered a farm in rural Kentucky without a search warrant.
They investigated the property and came upon a marijuana field surrounded on all sides by woods, fences, and
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owner’s curtilage, “the area to which extends the intimate activity associated with
the ‘sanctity of a man’s home and the privacies of life,’” which fall under the
scope of the Fourth Amendment’s protections.210
 Search Following Consent. A search to which an individual consents satisfies
Fourth Amendment requirements.211
 Roadblock-type Stops Unrelated to Border Crossings. As discussed later,
checkpoints may be established at or near the border to detect unlawful border
crossings.212 Government officers may also briefly stop and question individuals
without any suspicion of criminal activity at checkpoints to advance certain law
enforcement objectives.213 The Supreme Court has held that a sobriety
checkpoint was reasonable under the Fourth Amendment, given the state’s
interest in preventing driving under the influence of alcohol, the extent the
checkpoint advanced that interest, and the minimal intrusion on individuals who
were briefly stopped.214 In another decision, the Court held that a highway
checkpoint program with a primary purpose of discovering illegal narcotics
affronted the Fourth Amendment.215 In short, whether a checkpoint survives
Fourth Amendment scrutiny depends on a balancing of the competing interests at
stake and the effectiveness of the program.216
Warrantless Arrests
Although the Fourth Amendment generally requires law enforcement officers to obtain an arrest
warrant, an officer may lawfully arrest persons if the officer observes the arrestee committing an
offense or if the officer has probable cause to believe the arrestee has committed any felony.217
Indeed, INA Section 287(a) authorizes immigration officers to arrest aliens without a warrant in
certain circumstances—those in the act of unlawfully entering the country; those who an
immigration officer has “reason to believe” are unlawfully present in the United States and are
likely to escape before an arrest warrant can be obtained; and those reasonably suspected to have
committed a felony.218

embankment and hidden from public view. Id. at 173.
210 Id. at 180 (quoting Boyd v. United States, 116 U.S. 616, 630 (1886)).
211 Katz v. United States, 389 U.S. 347, 358 n.22 (1967).
212 See infra “Fixed Immigration Checkpoints.”
213 See City of Indianapolis v. Edmond, 531 U.S. 32, 37–38 (2000).
214 Michigan v. Sitz, 496 U.S. 444, 455 (1990).
215 Edmond, 531 U.S. at 48. The Court distinguished the narcotics checkpoint from the sobriety checkpoint in Sitz,
reasoning that the narcotics checkpoint program was indistinguishable from the general interest in crime control. Id.
at 41–42.
216 Id. at 47.
217 Michigan v. DeFillippo, 443 U.S. 31, 36 (1979) (holding that arrest by officer who observed conduct violating a
presumptively valid ordinance was not in violation of the Fourth Amendment).
218 See 8 U.S.C. § 1357(a) (conferring arrest authority to officers designated under prescribed regulations).
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Government Searches Beyond the Border and Its
Functional Equivalent
The Fourth Amendment’s warrant requirement generally does not apply to routine searches and
seizures at the border or its functional equivalent of persons arriving in the United States. The
government may conduct routine searches in these circumstances without probable cause or any
suspicion of unlawful activity. But the government’s border enforcement activities are not
confined to the physical border or its functional equivalent. For example, the government may
conduct searches and seizures in areas beyond the border to prevent unlawfully present aliens
who have evaded detection from traveling further into the interior of the United States, or to
prevent the importation of drugs and other contraband.219
In some circumstances, searches away from the border may be conducted without a judicial
warrant. For instance, courts have recognized that “extended border searches” can be conducted
of persons believed to have recently crossed the border and to be engaged in illegal activity.
Additionally, government officers may conduct other types of searches beyond the border that do
not necessarily require a physical entry into the United States. These searches include the
boarding of vessels along coastal waterways, “roving patrols” near the border, fixed immigration
checkpoints, and transportation checks.
Given their physical distance from the actual border, some of these searches may require at least
heightened suspicion or probable cause of unlawful activity to withstand Fourth Amendment
scrutiny.220
A table comparing the different types of warrantless searches and seizures that may occur at the
border and surrounding areas, including searches at the border or its functional equivalent,
immigration checkpoints, roving patrols, extended border searches, and the boarding of vessels,
can be found in Table A-3.
Extended Border Searches
While the doctrine has not been endorsed or applied by the Supreme Court, several lower courts
have concluded that the government may conduct warrantless, “extended border searches” of
certain individuals beyond the border or its functional equivalent.221 Courts have reasoned that
immigration and customs officials may not learn of criminal activity until after a vehicle or

219 See United States v. Villamonte-Marquez, 462 U.S. 579, 593 (1983) (recognizing the government’s interest in
patrolling inland or coastal waters “where the need to deter or apprehend smugglers is great”); United States v.
Martinez-Fuerte, 428 U.S. 543, 552 (1976) (“Although the Border Patrol maintains personnel, electronic equipment,
and fences along portions of the border, it remains relatively easy for individuals to enter the United States without
detection.”) (citing United States v. Brignoni-Ponce, 422 U.S. 873, 879 (1975)); Almeida-Sanchez v. United States,
413 U.S. 266, 268 (1973) (noting that the Border Patrol conducts inland surveillance activities “all in the asserted
interest of detecting the illegal importation of aliens”).
220 See, e.g., United States v. Singh, 415 F.3d 288, 294 (2d Cir. 2005) (“Border Patrol operations along inland routes—
not at the border or its functional equivalent—including permanent checkpoints, temporary checkpoints, and roving
patrols are held to a higher standard.”).
221 See United States v. Cardenas, 9 F.3d 1139, 1148 (5th Cir. 1993) (noting that “the border search doctrine has been
extended to allow government officials to conduct a warrantless search and seizure beyond the border or its functional
equivalent”); United States v. Caicedo-Guarnizo, 723 F.2d 1420, 1422 (9th Cir. 1984) (“The ‘extended border’ doctrine
is an expansion of this rule; it permits the Government to conduct border searches some time after the border has been
crossed.”).
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person has physically crossed the border, and that the government has a strong interest in
preventing importation of narcotics and contraband.222 Thus, unlike searches at a border’s
functional equivalent (e.g., an international airport), an extended border search occurs at some
point after an individual could have been first stopped from entering the United States.223
Yet because extended border searches occur after a person has entered the United States (and
potentially has already been inspected at the border), they intrude more upon a searched
individual’s privacy expectations than searches at the border or its functional equivalent, where
the government’s authority is more pronounced.224 Thus, lower courts have adopted a three-part
test to determine whether an extended border search is reasonable under the Fourth
Amendment.225 Under this test, an extended border search must meet these criteria:
1. “Reasonable certainty” (or a “high degree of probability”) that a border crossing
has occurred;
2. “reasonable certainty” that no change in the condition of the person or vehicle
being searched has occurred since the border crossing, and that any contraband
found was present when the person or vehicle crossed the border; and
3. reasonable suspicion of criminal activity.226

222 See Cardenas, 9 F.3d at 1149 (“The major impetus behind the extended border search doctrine is ‘the government
interest in stopping drug traffic.’ ”) (quoting WILLIAM E. RINGEL, SEARCHES AND SEIZURES, ARRESTS AND CONFESSIONS,
§ 15.3 (Supp. 1993)); United States v. Alfonso, 759 F.2d 728, 734 (9th Cir. 1985) (“Customs agents may learn or
realize the significance of suspicious circumstances only after a vehicle or person has crossed the border.”) (citing
Jones v. United States, 326 F.2d 124 (9th Cir. 1963)); United States v. Bilir, 592 F.2d 735, 740 (4th Cir. 1979) (“The
many difficulties that attend the attempt to intercept contraband and to apprehend increasingly mobile and sophisticated
smugglers at the very borders of the country have of course given birth to the doctrine.”). Additionally, “the agents may
delay a search in a reasonable effort to sweep in associates of suspected smugglers.” Alfonso, 759 F.2d at 734 (citing
United States v. Espericueta-Reyes, 631 F.2d 616, 619–20 (9th Cir. 1980)).
223 United States v. Guzman-Padilla, 573 F.3d 865, 878 (9th Cir. 2009) (citing United States v. Niver, 689 F.2d 520,
526 (5th Cir. 1982)); see also United States v. Stewart, 729 F.3d 517, 526 (6th Cir. 2013) (“Courts typically apply the
doctrine in situations where customs agents returned custody of an item, or where customs agents never took custody of
the item at the border, but conducted a subsequent search of that item after the custodian and the items had cleared
customs.”); United States v. Glaziou, 402 F.2d 8, 12–13 (2d Cir. 1969) (describing the “border area” as being “elastic”
and extending to the area “in the immediate vicinity of any entry point”). Courts have distinguished extended border
searches from functional border searches, particularly in criminal cases where the defendant argued that the
government search should have been subject to heightened scrutiny because it occurred away from the border. See, e.g.,
Stewart, 729 F.3d at 525–26 (concluding that defendant was not subject to an extended border search, even though one
of his laptop computers was examined at a CBP field office 20 miles from the airport, because his computer had not
been “cleared” for entry, and thus there was “no attenuation” between his border crossing and the search of his
computer); United States v. Cotterman, 709 F.3d 952, 961–62 (9th Cir. 2013) (holding that extended border search
doctrine did not apply to forensic examination of laptop computer at laboratory 170 miles from the border because the
computer “never cleared customs so entry was never effected”).
224 See Cotterman, 709 F.3d at 961 (“The key feature of an extended border search is that an individual can be assumed
to have cleared the border and thus regained an expectation of privacy in accompanying belongings.”); United States v.
Yang, 286 F.3d 940, 946 (7th Cir. 2002) (“The constitutional concern of extending the border in this manner is that it
potentially permits searches with less than probable cause at significant distances from our national borders.”); United
States v. Cardenas, 9 F.3d 1139, 1148 (5th Cir. 1993) (“An extended border search, however, entails a greater intrusion
on an entrant's legitimate expectations of privacy than does a search conducted at the border or its functional
equivalent.”).
225 Yang, 286 F.3d at 946 (“Because an extended border search entails greater intrusion on an entrant's legitimate
expectations of privacy than does a search conducted at the border or its functional equivalent, courts have instituted
the three-part test to ensure that the search is reasonable.”) (citing Cardenas, 9 F.3d at 1148).
226 See Stewart, 729 F.3d at 525; Guzman-Padilla, 573 F.3d at 878–79; Yang, 286 F.3d at 945; Cardenas, 9 F.3d
at 1148; United States v. Caminos, 770 F.2d 361, 364 (3d Cir. 1985); Alfonso, 759 F.2d at 734; United States v. Garcia,
672 F.2d 1349, 1364 (11th Cir. 1982). To determine whether there was “reasonable certainty” of a border crossing (or
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Courts have applied the three-pronged test when considering Fourth Amendment challenges to
extended border searches. For instance, in one case, the Ninth Circuit held that Border Patrol
agents lawfully searched a vehicle spotted near the U.S.-Mexico border.227 The court found there
was reasonable certainty that the driver had just crossed the border because his vehicle was
encountered in a remote area less than two miles from the border, accessible only through a valley
originating in Mexico.228 The Ninth Circuit concluded that the agents had reasonable suspicion
for the search because the vehicle was in a known smuggling route, had Mexican license plates,
drove erratically, and contained a black tarp covering in the back.229
In another case, the Fifth Circuit ruled that agents lawfully searched a woman encountered in El
Paso, Texas, just a block from a pedestrian border crossing.230 The court determined there was
reasonable certainty that the woman had just crossed the border because a checkpoint search of
her companion suggested they had been traveling together.231 The Fifth Circuit also found there
was reasonable certainty that there was no changed condition of the woman or her belongings
given the brief time and distance that had passed since she crossed the border and was
searched.232 The court further ruled there was reasonable suspicion to search the woman because
evidence seized from her companion indicated they were trafficking narcotics.233
Courts have upheld extended border searches on many other occasions.234 In a few cases, though,
courts have concluded that the challenged search did not meet the extended border search criteria.

“reasonable certainty” that the condition of the person or vehicle remained unchanged since the crossing), courts
consider the “totality of the surrounding circumstances,” such as the time and distance from the original entry and the
manner and extent of any surveillance. Guzman-Padilla, 573 F.3d at 879 (quoting Alexander v. United States, 362 F.2d
379, 382 (9th Cir. 1966)). The “reasonable certainty” standard is higher than probable cause, but does not require proof
beyond a reasonable doubt. Id. at 880 (citing United States v. Corral-Villavicencio, 753 F.2d 785, 788 (9th Cir. 1985));
United States v. Espinoza-Seanez, 862 F.2d 526, 531 (5th Cir. 1988) (citing United States v. Driscoll, 632 F.2d 737,
739 (9th Cir. 1980)). Instead, “the totality of the facts and circumstances within the officers’ knowledge and of which
they have reasonably trustworthy information [must] be sufficient in the light of their experience to warrant a firm
belief that a border crossing has occurred.” United States v. Tilton, 534 F.2d 1363, 1366–67 (9th Cir. 1976) (alteration
added). Thus, the officers are not required to show an absolute certainty of a border crossing. Guzman-Padilla, 573
F.3d at 880.
227 Guzman-Padilla, 573 F.3d at 880–82.
228 Id. at 881.
229 Id. at 882.
230 Cardenas, 9 F.3d at 1151–53.
231 Id. at 1151. In concluding there was a reasonable certainty that the woman had recently crossed the border, the court
observed that evidence of a border crossing “may be inferred from circumstantial evidence.” Id. at 1150 (internal
citation omitted).
232 Id. at 1152–53. The court held that the Border Patrol does not have to show there was “continuous surveillance” to
establish a reasonable certainty of an individual’s unchanged condition from the time of the border crossing, noting that
the court had previously upheld extended border searches where individuals were unobserved for up to 30 minutes or
close to an hour. Id. at 1152.
233 Id. at 1153. See also United States v. Alfonso, 759 F.2d 728, 735 (9th Cir. 1985) (“The fact that some search
occurred at the time of the initial border crossing simply does not prevent later searches from coming under the rules of
border searches.”) (citing United States v. Caicedo-Guarnizo, 723 F.2d 1420, 1422–23 (9th Cir. 1984)).
234 See, e.g., United States v. Villasenor, 608 F.3d 467, 472–74 (9th Cir. 2010) (ruling that search of individual’s
vehicle was proper because ICE agents had surveilled vehicle after it crossed the border, and they had received a tip
that the vehicle was being used for a drug trafficking operation); United States v. Yang, 286 F.3d 940, 947–49 (7th Cir.
2002) (upholding search of individual who had already passed through customs where it was undisputed that he had
just arrived at Chicago O’Hare International Airport; it was reasonably certain there was no change in the condition of
his luggage because it had been out of his control for a significant period of time; and there was reasonable suspicion
that he was trafficking narcotics); United States v. Espinoza-Seanez, 862 F.2d 526, 531–32 (5th Cir. 1988) (concluding
that search of automobile was reasonable because agents had noticed tracks leading to and from the border in an area
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For instance, the Ninth Circuit held that Border Patrol agents unlawfully searched a truck
suspected of carrying narcotics because they did not first see the truck until it was three miles
north of the border in the middle of a busy border town, and the Border Patrol agents could not
have been reasonably certain the truck or its cargo had recently crossed the border.235 Although
the agents learned afterward that the truck had been in the United States for only 90 minutes
before being spotted, “[t]he 90-minute gap in surveillance was enough to change the contents of
the truck, and therefore, the customs agents could not be reasonably certain any contraband found
in the truck had crossed the border.”236 Thus, the legality of an extended border search turns on
the specific facts and circumstances in each case.237
Boarding and Inspection of Vessels Within Interior and Coastal
Waterways
Government searches beyond the border are not strictly limited to land searches and seizures. The
federal government may also inspect vessels encountered within interior and coastal waterways.
Under federal statutes, customs officers may board vessels found “at any place in the United
States” or the “customs waters” (i.e., within 12 nautical miles from the coastline), to examine
documents, conduct inspections, and search the vessel and its cargo for contraband and other
potential federal customs violations.238 Additionally, Coast Guard officers (who also have
customs enforcement powers) have authority to board certain vessels in U.S. waters and the high
seas to examine documentation and conduct inspections and searches for potential violations of
federal law.239 For purposes of the Fourth Amendment, courts have treated the stopping of
waterborne vessels near the border differently than the stopping of automobiles on land, given a
vessel’s access to the open sea and the impracticability of establishing maritime checkpoints.240

where the vehicle had previously been seen, the agents had followed the vehicle both by helicopter and on the ground,
and there was reasonable suspicion of criminal activity); United States v. Alfonso, 759 F.2d 728, 736–37 (9th Cir.
1985) (holding that search of Colombian ship in Los Angeles harbor was permissible because it occurred within a day-
and-a-half after its arrival in U.S. waters and after an initial cursory search); United States v. Garcia, 672 F.2d 1349,
1367 (11th Cir. 1982) (upholding search of plane that had been under continuous surveillance after crossing the border
where there was reasonable suspicion that it was involved in drug smuggling); United States v. Bilir, 592 F.2d 735, 741
(4th Cir. 1979) (holding that agents reasonably searched individual some seven hours after an observed border crossing,
where the search had been delayed to confirm developing suspicion that the individual was engaged in drug
smuggling).
235 United States v. Perez, 644 F.2d 1299, 1302 (9th Cir. 1981).
236 Id. The court determined, moreover, that “government agents will not be allowed to justify an extended border
search with information which was not available to the agents at the time of the search.” Id. (citing United States v.
Ramos, 473 F. Supp. 1109, 1111 (S.D. Fla. 1979)). Given the inapplicability of the extended border search doctrine, the
court determined that the government failed to show that there was probable cause or consent for the vehicle search. Id.
at 1302–03; see also Almeida-Sanchez v. United States, 413 U.S. 266, 273 (1973) (holding that Border Patrol agents on
“roving patrol” must have probable cause to search a vehicle).
237 The Supreme Court has not addressed the concept of extended border searches. But, as discussed in this report, the
Court has addressed other types of interior enforcement activities occurring near the border that—unlike extended
border searches—do not necessarily require the physical crossing of the border. See United States v. Villamonte-
Marquez, 462 U.S. 579 (1983); United States v. Martinez-Fuerte, 428 U.S. 543 (1976); United States v. Ortiz, 422 U.S.
891 (1975); United States v. Brignoni-Ponce, 422 U.S. 873 (1975); Almeida-Sanchez v. United States, 413 U.S. 266
(1973).
238 19 U.S.C. §§ 482(a), 1581(a).
239 14 U.S.C. § 522(a). The statute requires the vessel to be “subject to the jurisdiction, or to the operation of any law,
of the United States.” Id.
240 See United States v. Villamonte-Marquez, 462 U.S. 579, 589 (1983) (“But no reasonable claim can be made that
permanent checkpoints would be practical on waters such as these where vessels can move in any direction at any time
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Thus, courts have interpreted the Fourth Amendment as permitting government officials, acting
under lawful authority, to board vessels without a warrant, probable cause, or any suspicion of
unlawful activity, so long as the boarding is limited in nature. But some courts have held that
government officers may not conduct more intrusive searches of the vessel without particularized
suspicion of a crime.
United States v. Villamonte-Marquez
In United States v. Villamonte-Marquez, the Supreme Court considered whether the Fourth
Amendment limits the government’s authority under federal statutes to board and inspect vessels
in U.S. waters further into the interior of the United States.241 In that case, customs officials
boarded a sailboat 18 miles inland from the Gulf coast to inspect documents, and they discovered
marijuana inside the vessel.242 The owners of the sailboat argued that boarding their vessel
without reasonable suspicion violated the Fourth Amendment.243 The government argued that 19
U.S.C. § 1581 authorized the boarding without suspicion.244
The Court rejected the Fourth Amendment challenge, reasoning that, since 1790, Congress has
authorized the suspicionless boarding of vessels, “reflecting its view that such boardings are not
contrary to the Fourth Amendment.”245 Additionally, the Court reasoned, although the Court has
required reasonable suspicion for “roving patrol” stops of vehicles near the border,246 “[t]he
nature of waterborne commerce in waters providing ready access to the open sea” made the
boarding of vessels distinguishable.247 The Court observed that, unlike vehicle stops, there is no
practical alternative of stopping all vessels at permanent water checkpoints.248 The Court
concluded that the government’s interest in assuring compliance with vessel documentation
requirements, particularly in heavy drug trafficking areas, outweighed any “modest intrusion”
from boarding a vessel.249 The Court thus held that government officers may board vessels on

and need not follow established ‘avenues’ as automobiles must do. Customs officials do not have as a practical
alternative the option of spotting all vessels which might have come from the open sea and herding them into one or
more canals or straits in order to make fixed checkpoint stops.”); Cross v. Mokwa, 547 F.3d 890, 900 (8th Cir. 2008)
(“The Supreme Court expressly distinguished searches of such sea vessels from those of automobiles on land.”).
241 Villamonte-Marquez, 462 U.S. at 581 (“We are asked to decide whether the Fourth Amendment is offended when
Customs officials, acting pursuant to this statute and without any suspicion of wrongdoing, board for inspection of
documents a vessel that is located in waters providing ready access to the open sea.”).
242 Id. at 583.
243 Id. at 585.
244 Id.
245 Id. at 592. The Court described a 1790 statute authorizing the boarding of vessels as a “lineal ancestor” to 19 U.S.C.
§ 1581. Villamonte-Marquez, 462 U.S. at 584. According to the Court, “the enactment of this statute by the same
Congress that promulgated the constitutional amendments that ultimately became the Bill of Rights gives the statute an
impressive historical pedigree.” Id. at 585.
246 See United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975) (requiring reasonable suspicion for roving patrol
stops near the border); compare with United States v. Martinez-Fuerte, 428 U.S. 543, 562, 566 (1976) (holding that
fixed checkpoint stops near the border require no reasonable suspicion). For additional discussion about roving patrols
and immigration checkpoints in the interior of the United States, see infra “Roving Patrols” & “Fixed Immigration
Checkpoints.”
247 Villamonte-Marquez, 462 U.S. at 588–89.
248 Id. at 589. In addition, “[t]he system of prescribed outward markings used by States for vehicle registration is also
significantly different than the system of external markings on vessels, and the extent and type of documentation
required by federal law is a good deal more variable and more complex than are the state vehicle registration laws.” Id.
at 593.
249 Id. at 592. The Court described the routine customs inspections as “a brief detention where officials come on board,
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inland waters with ready access to the open sea for routine document checks without suspicion of
unlawful activity.250
Lower Courts’ Decisions on Boarding of Vessels
Lower courts have also recognized the government’s broad authority to board vessels and
conduct routine inspections without a warrant or any individualized suspicion.251 Courts have
held that, during the inspection, the officers may visit public areas of the vessel and observe
anything in plain view.252 But officers must have at least reasonable suspicion to conduct a more
intrusive search of the vessel, and probable cause for an exhaustive “stem to stern” search.253
While the government’s ability to conduct warrantless searches of vessels within interior or
coastal waterways is generally limited to routine safety and document inspections (unless there is
particularized suspicion of unlawful activity), the authority to board and search vessels crossing
the international border is less restrained.254 Lower courts have recognized that, if a vessel is
believed to have recently crossed the border into the United States, customs officials generally

visit public areas of the vessel, and inspect documents.” Id.
250 Id. at 593.
251 See, e.g., United States v. Albano, 722 F.2d 690, 695 (11th Cir. 1984) (“Customs officers may board a vessel in
Customs waters to check its documents even if the boarding serves merely as a pretext for the officers’ desire to look
for signs of contraband.”); United States v. Helms, 703 F.2d 759, 762–63 (4th Cir. 1983) (“Customs officers are, by
express statute, authorized to stop and board for a documentary examination any vessel within the ‘customs waters,’ . . .
with or without any suspicion of criminal activity.”); United States v. Watson, 678 F.2d 765, 771 (9th Cir. 1982)
(declaring that “the Coast Guard has plenary authority to stop vessels for document and safety inspections” without any
suspicion); United States v. Hilton, 619 F.2d 127, 131 (1st Cir. 1980) (“We believe the limited intrusion represented by
a document and safety inspection on the high seas, even in the absence of a warrant or suspicion of wrongdoing, is
reasonable under the fourth amendment.”); United States v. Freeman, 579 F.2d 942, 946 (5th Cir. 1978) (“The
reasonableness and constitutionality of brief stops of vessels in Customs waters by Customs agents for the purpose of
routine document and safety checks is beyond question.”).
252 See United States v. Cardona-Sandoval, 6 F.3d 15, 23 (1st Cir. 1993) (stating that the inspection “must be confined
to areas reasonably incident to the purpose of the inspection”); United States v. Humphrey, 759 F.2d 743, 746 (9th Cir.
1985) (concluding that routine Coast Guard inspection was limited to publicly exposed deck area and did not extend to
living quarters below deck); United States v. Herrera, 711 F.2d 1546, 1550 n.6 (11th Cir. 1983) (“At a minimum, it
allows Customs officers to view those non-private areas of the vessel which are in the plain view of a lawful boarding
party.”); United States v. Garcia, 598 F. Supp. 533, 537 (S.D. Fla. 1984) (“Once properly aboard a vessel, officers are
given a considerable opportunity to detect illegal activity. They may visit public areas of the boat and observe anything
in plain view.”).
253 See Cardona-Sandoval, 6 F.3d at 23 (stating that reasonable suspicion authorizes only a “limited intrusion” of
vessel); United States v. Roy, 869 F.2d 1427, 1430 (11th Cir. 1989) (“A full stem to stern search is permissible on
probable cause that a crime has been, or is being, committed.”); Herrera, 711 F.2d at 1550 (“We hold today that where
Customs officers have a reasonable suspicion that Customs violations exist, they may board a vessel to conduct a
limited ‘search’ of the non-private areas of the vessel.”); Hilton, 619 F.2d at 131 (“A more extensive search is
permissible only if there is consent or probable cause to believe a crime has been or is being committed.”); United
States v. Williams, 617 F.2d 1063, 1087 (5th Cir. 1980) (holding that the Fourth Amendment requires at least
reasonable suspicion to search a vessel); Garcia, 598 F. Supp. at 537 (“Once properly aboard a vessel, officers cannot
conduct an exhaustive search unless by the time their limited inspection is complete their suspicions have ripened into
probable cause.”).
254 See United States v. Alfonso, 759 F.2d 728, 734 (9th Cir. 1985) (“The rules of the ‘border search’ extend to
crossings of ocean boundaries as well as the land boundaries with Mexico and Canada.”); Blair, 665 F.2d at 505 (“The
requirements that the fourth amendment’s reasonableness standard imposes upon a vessel seizure vary greatly
according to that vessel’s geographic location.”).
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may stop and search the vessel beyond the scope of a routine document inspection with no
suspicion that a crime is afoot.255
Roving Patrols
The U.S. Border Patrol frequently conducts “roving patrols” near the border to enforce federal
immigration and drug laws.256 A roving patrol occurs when Border Patrol agents traverse certain
areas near the border and stop vehicles suspected of carrying unlawfully present aliens or illegal
narcotics, even if there is not necessarily an indication the vehicle had crossed the border.257
Unlike immigration checkpoints discussed later in this report—which occur at established points
on roads near the border and may require all drivers to stop for brief questioning258—roving
patrols do not occur at fixed locations and only target those suspected of engaging in unlawful
activity.259 Additionally, unlike extended border searches, roving patrols may stop vehicles
regardless of whether the vehicle and its occupants had crossed the border, and regardless of
whether the condition of the vehicle and its occupants had changed since a border crossing.
As discussed below, the Supreme Court and lower courts have addressed the constitutional
limitations on roving patrols, concluding that Border Patrol officers may randomly stop vehicles
near the border so long as they have reasonable suspicion that the occupants are engaged in
unlawful activity (e.g., smuggling aliens). But the officers may not search the vehicle in the
absence of probable cause or consent.

255 See United States v. Alfaro-Moncada, 607 F.3d 720, 732 (9th Cir. 2010) (holding that customs officers could search
living quarters inside foreign cargo ship docked at a port of entry without any suspicion); United States v. Pickett, 598
F.3d 231, 235 (5th Cir. 2010) (“Our precedent establishes that a border crossing occurs whenever a vessel crosses from
international waters into the United States, regardless of the defendant's departure point.”); United States v. Dobson,
781 F.2d 1374, 1376 (9th Cir. 1986) (“Customs officials may thus conduct a border search of any ship arriving in port
which is known to have sailed from international waters.”); Herrera, 711 F.2d at 1552 (“Our cases have clearly
distinguished between border searches which are reasonable because they occur at the border and limited Customs
searches in the maritime context which are reasonable if based on a reasonable suspicion of Customs violations.”);
United States v. Helms, 703 F.2d 759, 763 (4th Cir. 1983) (explaining that stopping and boarding a vessel in inland or
coastal waterways is deemed to occur at the border’s functional equivalent if the vessel had recently crossed the
border).
256 See Martinez-Fuerte, 428 U.S. at 552 (noting that “roving patrols are maintained to supplement the [immigration]
checkpoint system”). While such patrols normally take place in the vicinity of the border, there are some instances
when they have been conducted at more considerable distances. See United States v. Venzor-Castillo, 991 F.2d 634,
634–35, 639–40 (10th Cir. 1993) (holding that a Border Patrol stop of a vehicle some 235 miles from the border did not
occur within a reasonable distance permitted under statute).
257 See United States v. Ortiz, 422 U.S. 891, 894 (1975) (noting that roving patrols “often operate at night on seldom-
traveled roads” and “look for criminal activity, both alien smuggling and contraband smuggling”).
258 See Martinez-Fuerte, 428 U.S. at 558–60 (describing the “regularized manner” of routine checkpoint stops).
259 See Moving the Line of Scrimmage: Re-Examining the Defense-In-Depth Strategy, Hearing Before the Subcomm. on
Border and Maritime Sec. of the H. Comm. on Homeland Sec., 114th Cong. (2016) (written testimony of U.S. Border
Patrol Chief Mark Morgan) (“Generally, Border Patrol agents employ two means to stop vehicles driven by smugglers
using side roads to circumvent a checkpoint: additional checkpoints and roving patrols. USBP may establish and
coordinate tactical checkpoints on circumvention routes, so as to ensure the effectiveness of checkpoints on main
thoroughfares. USBP may also conduct roving patrols, an acceptable and effective means to stop vehicles driven by
smugglers using side roads to circumvent an immigration checkpoint. Border Patrol agents on roving patrol may stop a
vehicle only if they have reasonable suspicion, based upon specific articulable facts and rational inferences from those
facts, that the vehicle contains individuals who may have illegally entered the United States.”).
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Almeida-Sanchez v. United States
In Almeida-Sanchez v. United States, the Supreme Court addressed the constitutionality of roving
patrols under the Fourth Amendment.260 In that case, the Border Patrol had stopped a motorist
some 25 air miles north of the U.S.-Mexico border and found marijuana inside his vehicle.261 The
motorist, who was convicted of illegally transporting marijuana, argued that the officers lacked
probable cause and that the search of his vehicle therefore violated the Fourth Amendment.262 In
response, the government argued that the vehicle search was permissible under INA Section
287(a)(3), which authorizes warrantless searches of vehicles and other conveyances within a
“reasonable distance” of the border.263
The Supreme Court held that the search of the vehicle violated the Fourth Amendment.264
Recognizing the federal government’s authority to conduct routine inspections and searches at the
border without a warrant or probable cause, the Court determined that roving patrol searches of
vehicles at points removed from the physical border or its functional equivalent “was of a wholly
different sort.”265 The Court reasoned that the government’s interests at the border are less potent
in the interior of the United States, where individuals have greater Fourth Amendment protections
against governmental intrusion.266 The Court concluded that such searches required either
probable cause or consent to the search.267
United States v. Brignoni-Ponce
The Almeida-Sanchez Court considered whether roving patrol searches, in which Border Patrol
agents search vehicles for evidence of illegal activity, were permissible under the Fourth
Amendment. In United States v. Brignoni-Ponce, the Court considered the constitutionality of
roving patrol stops, in which agents stop vehicles for the more limited purpose of questioning the
occupants about immigration status and any suspicious circumstances.268 In that case, Border
Patrol agents stopped a vehicle because the occupants appeared to be of Mexican descent.269
Upon questioning the driver and his two passengers, the agents learned they had entered the

260 Almeida-Sanchez v. United States, 413 U.S. 266, 269 (1973).
261 Id. at 267–68.
262 Id.
263 Id. at 268; see also 8 U.S.C. § 1357(a)(3) (authorizing immigration officers to engage in warrantless search of
vehicle “within a reasonable distance from any external boundary of the United States”); 8 C.F.R. § 287.1(a)(2)
(defining “reasonable distance” as “within 100 air miles from any external boundary of the United States or any shorter
distance which may be fixed by” the Border Patrol).
264 Almeida-Sanchez, 413 U.S. at 272–73.
265 Id. at 273.
266 Id. at 274–75.
267 Id. The Court observed that, although it had previously held that the government may stop and search an automobile
without a warrant, see, e.g., Carroll v. United States, 267 U.S. 132 (1925), that exception “does not declare a field day
for the police in searching automobiles.” Almeida-Sanchez, 413 U.S. at 269. “Automobile or no automobile, there must
be probable cause for the search.” Id. The Court also determined that, although it had previously ruled that the
government may conduct certain types of administrative inspections on less than probable cause, see Camara v.
Municipal Ct., 387 U.S. 523 (1967), United States v. Biswell, 406 U.S. 311 (1972), Colonnade Catering Corp. v.
United States, 397 U.S. 72 (1970), those decisions were inapposite because they still required the government inspector
to obtain a warrant before conducting the search; and they involved inspections of federally licensed and regulated
commercial enterprises. Almeida-Sanchez, 413 U.S. at 270–71.
268 United States v. Brignoni-Ponce, 422 U.S. 873, 874 (1975).
269 Id. at 875.
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United States unlawfully and arrested them.270 The driver, who was convicted of illegally
transporting aliens,271 argued that he was subject to an unlawful seizure.272 The government
argued that it had authority to conduct the stop without a warrant or any particularized suspicion
under the INA.273 The government further argued that preventing the unlawful entry of aliens into
the United States warranted roving patrols near the border.274
The Supreme Court determined that suspicionless roving patrol stops would risk “potentially
unlimited interference” with border-area residents’ use of the highways.275 The Court determined
that the “reasonable suspicion” standard should apply to roving patrol stops given their “modest
intrusion.”276 Thus, the Court held, “officers on roving patrol may stop vehicles only if they are
aware of specific articulable facts, together with rational inferences from those facts, that
reasonably warrant suspicion that the vehicles contain aliens who may be illegally in the
country.”277 According to the Court, the stop must be limited to asking about citizenship or
immigration status, and any suspicious circumstances.278 “[A]ny further detention or search must
be based on consent or probable cause.”279
The Court listed the criteria to determine whether there is reasonable suspicion for a roving patrol
stop, including the characteristics of the area in which the vehicle is found; the vehicle’s
proximity to the border; the usual traffic patterns on the particular road where the vehicle is
encountered; the driver’s behavior (e.g., erratic driving or attempts to evade the officers); recent
unlawful border crossings in the area; aspects of the vehicle itself (e.g., if it contains large

270 Id.
271 See 8 U.S.C. § 1324(a)(2) (prohibiting a person from knowingly or recklessly bringing into the United States an
alien who has not received authorization to enter the country).
272 Brignoni-Ponce, 422 U.S. at 875.
273 Id. at 876–77; see 8 U.S.C. § 1357(a)(1) (authorizing an immigration officer “to interrogate any alien or person
believed to be an alien as to his right to be or to remain in the United States” without a warrant) and (a)(3) (authorizing
warrantless boarding and searching of vehicles and other conveyances “within a reasonable distance” from the border).
274 Id. at 878–79.
275 Id. at 882. The Court observed that “[r]oads near the border carry not only aliens seeking to enter the country
illegally, but a large volume of legitimate traffic as well,” and that there are metropolitan areas near the U.S.-Mexico
border with significantly large populations, such as San Diego, California. Id. The Court warned that if there were no
restrictions on the Border Patrol’s ability to conduct roving patrol stops, its agents “could stops motorists at random for
questioning, day or night, anywhere within 100 air miles of the 2,000-mile border, on a city street, a busy highway, or a
desert road, without any reason to suspect that they have violated any law.” Id. at 883.
276 Id. at 879–81. The Court cited its prior decisions in Terry v. Ohio, 392 U.S. 1 (1968), and Adams v. Williams, 407
U.S. 143 (1972), which applied the reasonable suspicion standard to brief investigatory stops, and stated that those
cases “establish that in appropriate circumstances the Fourth Amendment allows a properly limited ‘search’ or ‘seizure’
on facts that do not constitute probable cause to arrest or to search for contraband or evidence of crime.” Brignoni-
Ponce, 422 U.S. at 881. The Court concluded that applying this standard “allows the Government adequate means of
guarding the public interest and also protects residents of the border areas from indiscriminate official interference.” Id.
at 883.
277 Id. at 884; see also Delaware v. Prouse, 440 U.S. 648, 663 (1979) (holding that the police may not randomly stop an
automobile to check driver’s license and registration unless there is reasonable suspicion that the motorist is unlicensed
or that the automobile is not registered, or that either the vehicle or an occupant is otherwise subject to seizure for
violation of law). While the Court concluded that roving patrol stops require reasonable suspicion that a vehicle is
carrying unlawfully present aliens, the Court did not decide whether, more generally, immigration officers may stop
individuals who are reasonably believed to be aliens, when there is no reasonable suspicion of their unlawful presence.
Brignoni-Ponce, 422 U.S. at 884 n.9.
278 Id. at 881.
279 Id. at 882; see also Almeida-Sanchez v. United States, 413 U.S. 266, 273 (1973) (holding that a roving patrol search
of an automobile requires probable cause or consent to the search).
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compartments, appears to be heavily loaded, or carries a large number of passengers); and the
physical characteristics or appearance of the persons inside the vehicle.280
The Court ruled that the Border Patrol agents lacked reasonable suspicion because they relied
solely on the apparent Mexican ancestry of the vehicle’s occupants.281 The Court stated that the
occupants’ Mexican ancestry in itself failed to provide a reasonable belief that they were aliens or
that the vehicle concealed unlawfully present aliens.282 While the Court suggested that ethnic
appearance is a “relevant factor” in the reasonable suspicion calculus, “standing alone it does not
justify stopping all Mexican-Americans to ask if they are aliens.”283
United States v. Cortez
The Supreme Court has applied Brignoni-Ponce’s reasonable suspicion test in other roving patrol
cases. In United States v. Cortez, the Court considered whether Border Patrol agents in a remote
part of Arizona lawfully stopped a camper believed to be smuggling aliens into the United
States.284 The Court clarified that reviewing courts should look to the “totality of the
circumstances” to determine whether the agents have reasonable suspicion.285 The Court held
there was reasonable suspicion for the stop because the agents had previously uncovered clues of
alien smuggling activity in the area, and knew where the suspects would likely appear.286 The
Court’s decision in Cortez signaled that no single factor is dispositive in analyzing the
reasonableness of a roving patrol stop. Instead, courts must consider whether all the factors relied
upon by the agent—including any reasonable inferences drawn from those facts—collectively
establish reasonable suspicion.
United States. v. Arvizu
In United States v. Arvizu, the Supreme Court held that a Border Patrol agent in Arizona had
reasonable suspicion to stop a minivan found to be carrying more than 100 pounds of
marijuana.287 The agent had observed the van on a remote road often used by smugglers and
noticed the van suddenly slow down upon approaching him.288 The agent also observed that the
van had five occupants, the driver failed to acknowledge him, and two children were seated as
though propped up on concealed cargo.289 In addition, the van was registered to an address in an

280 Brignoni-Ponce, 422 U.S. at 884–85.
281 Id. at 885–86.
282 Id. at 886. The Court noted that many U.S. citizens have physical characteristics associated with Mexican ancestry,
and that even in border areas a relatively small number of those with Mexican ancestry are aliens. Id.
283 Id. at 887. For more discussion about the use of race or ethnic appearance in making roving patrol stops (“racial
profiling”), see infra “Racial Profiling.”
284 United States v. Cortez, 449 U.S. 411, 412–13 (1981).
285 Id. at 417–18; see also United States v. Moreno-Chaparro, 180 F.3d 629, 631–32 (5th Cir. 1998) (“No single factor
is determinative; the totality of the particular circumstances must govern the reasonableness of any stop by roving
border patrol officers.”). According to the Supreme Court, there must be consideration of “all the circumstances” in the
case, including the officers’ objective observations, information from police reports, the suspect’s patterns of criminal
behavior, and the reasonable inferences and deductions drawn from those facts. Cortez, 449 U.S. at 418. In addition,
the circumstances “must raise a suspicion that the particular individual being stopped is engaged in wrongdoing.” Id.
286 Cortez, 449 U.S. at 413–15, 417, 419–21.
287 United States v. Arvizu, 534 U.S. 266, 277–78 (2002).
288 Id. at 269–70.
289 Id. at 270.
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area known for alien and drug smuggling.290 The Court concluded that the officer’s observations,
when “taken together,” raised a reasonable inference of criminal activity.291 The Court’s decision
in Arvizu reinforced that courts must consider the totality of the circumstances in assessing
whether facts relied upon by Border Patrol agents demonstrate reasonable suspicion.
Lower Court Decisions on Roving Patrols
Lower courts, when applying the Brignoni-Ponce factors to roving patrol stop challenges,292 have
generally concluded that the challenged stops were supported by reasonable suspicion.293 In a few
cases, however, reviewing courts determined that Border Patrol agents lacked reasonable
suspicion for the stop. For instance, the Fifth Circuit has ruled that reasonable suspicion was
absent when a truck was stopped more than 200 miles from the border, there was a piece of brush
under the truck that could have been picked up “in myriad unsuspicious ways,” and the vehicle
occupants avoided eye contact but engaged in no other suspicious behavior.294 Similarly, the
Ninth Circuit held that Border Patrol agents tailgating a vehicle failed to establish reasonable
suspicion when the driver of the vehicle changed lanes and pulled off the main road, and tried to
shield his face from the patrol car’s headlights.295 As these cases show, the reasonable suspicion
determination is a fact-intensive inquiry that depends on the circumstances in each case.296

290 Id. at 271.
291 Id. at 277–78. The Ninth Circuit had determined that most of the factors the Border Patrol officer relied upon to
make the vehicle stop carried little or no weight, and that the remaining factors failed to establish reasonable suspicion.
Id. at 272–73. The Supreme Court held that the Ninth Circuit erroneously evaluated these factors “in isolation from
each other” rather than considering the “totality of the circumstances.” Id. at 274. Although the factors, by themselves,
may have been “consistent with innocent travel,” they collectively established a “particularized and objective basis” for
the vehicle stop. Id. at 275, 277–78.
292 With regard to the proximity to the border factor, the U.S. Court of Appeals for the Fifth Circuit has held that this
element is satisfied if a vehicle is spotted less than 50 miles from the border (even if it was later stopped more than 50
miles from the border). United States v. Freeman, 914 F.3d 337, 343 (5th Cir. 2019). Vehicles traveling more than 50
miles from the border, on the other hand, are considered to be a “substantial distance” from the border. United States v.
Garza, 727 F.3d 436, 441 (5th Cir. 2013) (citing United States v. Inocencio, 40 F.3d 716, 722 n.7 (5th Cir. 1994)).
Thus, in the Fifth Circuit, roving patrols occurring less than 50 miles from the border implicate the proximity factor,
and “this ‘vital element’ contributes significantly to the reasonableness of the Border Patrol agents’ suspicion.” United
States v. Nichols, 142 F.3d 857, 867 (5th Cir. 1998).
293 See, e.g., United States v. Raygoza-Garcia, 902 F.3d 994, 1000–01 (9th Cir. 2018) (officers had reasonable
suspicion where vehicle was encountered 70 miles from the border, the vehicle had changed drivers since it was
observed earlier in the day, the driver rapidly slowed down and became rigid upon noticing the officers, and the driver
focused on the officers as they followed him close behind); United States v. Garza, 727 F.3d 436, 440–42 (5th Cir.
2013) (officer had reasonable suspicion to stop truck because it was traveling along a well-known smuggling route, it
contained a sheet of plywood over the truck bed, and the driver became excited and nervous upon noticing the patrol
car); United States v. Cheromiah, 455 F.3d 1216, 1221–22 (10th Cir. 2006) (stop was permissible because van was
encountered 85 miles from border in area frequented by smugglers, the van had a temporary license plate, the van’s
driver and front passenger stiffened up and avoided eye contact with the agent, and the agent saw one passenger in the
back of the van “diving” down); United States v. Singh, 415 F.3d 288, 295 (2d Cir. 2005) (reasonable suspicion
established where vehicle in rural area known for alien smuggling activity drove very slowly and tapped its brakes in a
manner commonly used to signal a car’s availability to pick up aliens, and vehicle later contained passengers just
minutes after motion sensors had alerted to a border crossing); United States v. Cruz-Hernandez, 62 F.3d 1353, 1355–
56 (11th Cir. 1995) (agent lawfully stopped van because the driver appeared nervous and quickly averted his gaze when
the agent approached, the agent knew that many “undocumented aliens” lived in a nearby trailer park, and the driver
was wearing clothes typically worn by “undocumented aliens” working in the local fields).
294 United States v. Olivares-Pacheco, 633 F.3d 399, 402–05 (5th Cir. 2011).
295 United States v. Sigmond-Ballesteros, 285 F.3d 1117, 1122–26 (9th Cir. 2002).
296 Compare, e.g., United States v. Cervantes, 797 F.3d 326, 338–39 (5th Cir. 2015) (holding that there was reasonable
suspicion when a vehicle appeared to be sagging in the rear; the vehicle suddenly changed lanes and decelerated when
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Fixed Immigration Checkpoints
The Border Patrol also establishes immigration checkpoints near the border. An immigration
checkpoint, unlike a roving patrol, occurs at stationary points on major highways.297 The Border
Patrol operates two types of checkpoints: permanent checkpoints, which “are maintained at or
near intersections of important roads leading away from the border”; and temporary (or
“tactical”) checkpoints which “operate like permanent ones, [and] occasionally are established in
other strategic locations.”298 In some checkpoints, Border Patrol officers may require all drivers to
stop for brief questioning.299 In other checkpoints, officers may stop only some motorists and
refer them to a “secondary inspection” area for questioning.300
Immigration checkpoints are distinguishable from border checkpoints, which are located in areas
where passing traffic has likely crossed the international border, and which are considered the
border’s functional equivalent.301 Immigration checkpoints, in contrast, are typically located on
roads leading away from the border where traffic has not necessarily crossed the border.302

officers approached; the driver did not respond to the officers’ attempt to get their attention; the rear passengers were
dirty and unshaven; and one of the passengers sat in the rear cargo area of the vehicle); United States v. Valdes-Vega,
738 F.3d 1074, 1079–80 (9th Cir. 2013) (concluding that reasonable suspicion was present when a truck was traveling
on a highway frequently used by smugglers; the truck had Mexican license plates; and agents saw the truck speeding,
changing lanes frequently, and cutting off other traffic); with United States v. Rangel-Portillo, 586 F.3d 376, 380–83
(5th Cir. 2009) (fact that vehicle passengers leaving a Wal-Mart parking lot all wore seatbelts, sat rigidly, refrained
from talking to each other, had no shopping bags, and did not make eye contact with agent did not establish reasonable
suspicion even though stop occurred just 500 yards from the border); United States v. Garcia-Camacho, 53 F.3d 244
(9th Cir. 1995) (reasonable suspicion not shown based on mere fact that motorists appeared Hispanic, happened to be
traveling on a highway used by “illegal aliens,” looked straight ahead and did not acknowledge the agent, drove a truck
that appeared “heavily ladened,” and engaged in other common behavior that matched many law-abiding users of the
highway); United States v. Martinez-Cigarroa, 44 F.3d 908, 911 (10th Cir. 1995) (no reasonable suspicion to stop
vehicle based on evidence that driver appeared to show an interest in a passing van and a Border Patrol car following
that van).
297 See United States v. Martinez-Fuerte, 428 U.S. 543, 558–60 (1976) (describing the “regularized manner” of routine
checkpoint stops); United States v. Ortiz, 422 U.S. 891, 892 (1975) (noting that traffic checkpoints “differ from roving
patrols in several important respects.”).
298 Martinez-Fuerte, 428 U.S. at 552.
299 See id. at 550 (describing checkpoint near Sarita, Texas, where “the officers customarily stop all northbound
motorists for a brief inquiry.”); United States v. Ortiz, 422 U.S. 891, 894 (1975) (noting that in checkpoints where
traffic is light “officers can stop all vehicles for questioning and routinely inspect more of them” than in other
checkpoints).
300 See Martinez-Fuerte, 428 U.S. at 546 (describing checkpoint near San Clemente, California, where most motorists
“are allowed to resume their progress without any oral inquiry or close examination,” but some may be directed to a
“secondary inspection” area for questioning about their citizenship and immigration status); Ortiz, 422 U.S. at 893–94
(“If anything about a vehicle or its occupants leads an officer to suspect that it may be carrying aliens, he will stop the
car and ask the occupants about their citizenship.”).
301 See United States v. Jackson, 825 F.2d 853, 860 (5th Cir. 1987) (noting that “border equivalent checkpoints
intercept no more than a negligible number of domestic travelers”).
302 Id. at 859 (explaining that vehicles on roads leading away from the border may not have crossed the border). The
location of an immigration checkpoint is based on various factors, including whether the location is (1) distant enough
from the border to avoid interference with traffic in populated areas near the border (e.g., to avoid repeated checking of
commuter or urban traffic); (2) near the confluence of two or more major roads leading away from the border; (3) in
terrain that restricts passage of vehicles around the checkpoint (e.g., mountains); (4) in a stretch of highway that
ensures safe operation of the checkpoint (e.g., having an unrestricted view of oncoming traffic, avoiding congestion);
and (5) located more than 25 miles from the border. Martinez-Fuerte, 428 U.S. at 553. The 25-mile factor is based on
DHS regulations that allow Mexican nationals who have been issued Border Crossing Cards to enter the United States
without obtaining an I-94 “Arrival/Departure Record” so long as their visit is limited to within 25 miles of the U.S.-
Mexico border (currently 75 miles if the alien is visiting Arizona, and 55 miles if the alien is visiting New Mexico). See
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Consequently, because immigration checkpoints occur in places beyond the point at which a
person could have entered the United States, they are distinguishable from stops at the border or
its functional equivalent. Immigration checkpoints are also distinct from extended border
searches, which may also occur in the interior of the United States, because they do not require
evidence of a border crossing.
In reviewing constitutional challenges to immigration checkpoints, the Supreme Court and lower
courts have generally considered whether such stops are permissible under the Fourth
Amendment. Courts have generally determined that checkpoint stops are reasonable without a
warrant or any individualized suspicion of unlawful activity given the regularized and limited
nature of such stops. But courts have determined that more intrusive checkpoint stops (e.g., an
extended detention or vehicle search) may require reasonable suspicion or probable cause.
United States v. Martinez-Fuerte
In United States v. Martinez-Fuerte, the Supreme Court held that immigration checkpoint stops
require no individualized suspicion under the Fourth Amendment.303 The Court reasoned that
there is a strong public interest for routine checkpoints “because the flow of illegal aliens cannot
be controlled effectively at the border.”304 The Court also observed that routine checkpoint stops
are typically brief detentions that are “limited to what can be seen without a search.”305
The Court recognized that, in Brignoni-Ponce, it had imposed a reasonable suspicion standard for
roving patrol stops, but determined that immigration checkpoints are less intrusive.306 Given the
“regularized manner” of immigration checkpoints, the Court reasoned, motorists “are not taken
by surprise” when they see them, and can be reasonably certain that the stops are authorized.307
Additionally, at immigration checkpoints, “there is less room for abusive or harassing stops of
individuals than there was in the case of roving-patrol stops.”308
The Court thus held that the Border Patrol may stop and briefly question motorists at “reasonably
located” checkpoints.309 The Court also determined that Border Patrol agents may, while

8 C.F.R. §§ 212.1(c)(1), 235.1(h)(1)(iii), (v). The checkpoints are established beyond this 25-mile zone “in order to
control the unlawful movement inland of such visitors.” United States v. Baca, 368 F. Supp. 398, 406 (S.D. Fla. 1973).
303 Martinez-Fuerte, 428 U.S. at 545.
304 Id. at 556. The Court noted that checkpoints deter smugglers and aliens who had surreptitiously entered the United
States from traveling farther into the interior. Id. at 557. The Court determined that requiring reasonable suspicion for
routine checkpoint stops “would be impractical because the flow of traffic tends to be too heavy to allow the
particularized study of a given car that would enable it to be identified as a possible carrier of illegal aliens.” Id.
305 Id. at 557–58.
306 Id. at 558–59.
307 Id. at 559. The Court explained that “[t]he location of a fixed checkpoint is not chosen by officers in the field, but by
officials responsible for making overall decisions as to the most effective allocation of limited enforcement resources.
We may assume that such officials will be unlikely to locate a checkpoint where it bears arbitrarily or oppressively on
motorists as a class.” Id.; see also United States v. Ortiz, 422 U.S. 891, 894–95 (1975) (“At traffic checkpoints the
motorist can see that other vehicles are being stopped, he can see visible signs of the officers’ authority, and his is
much less likely to be frightened or annoyed by the intrusion.”).
308 Martinez-Fuerte, 428 U.S. at 559. The Court also rejected the claim that checkpoints that refer only some motorists
to a “secondary inspection” area for questioning are more intrusive, noting that such referrals are limited to relatively
routine inquiries “that cannot feasibly be made of every motorist where the traffic is heavy.” Id. at 560. In short,
because “selective referrals” do not require all passing motorists to be questioned, they “tend to advance some Fourth
Amendment interests by minimizing the intrusion on the general motoring public.” Id.
309 Id. at 562, 566. The Court stated that the reasonableness of checkpoint stops depends on factors such as the location
of the checkpoint and its method of operation. Id. at 565. But “the choice of checkpoint locations is an administrative
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conducting checkpoints, selectively refer motorists to a “secondary inspection” area based on
criteria that would not justify a roving patrol stop, including ethnic appearance.310 Because the
checkpoint stop’s minimal intrusion requires no particularized suspicion, the Court reasoned,
“officers must have wide discretion” to “divert” motorists for questioning.311 The Court cautioned
that a checkpoint stop must be limited in scope and duration, and any further intrusion requires
heightened suspicion or consent.312
United States v. Ortiz
The Supreme Court has also considered the constitutionality of warrantless vehicle searches at
immigration checkpoints.313 In United States v. Ortiz, Border Patrol agents had stopped a vehicle
at a southern California checkpoint, and discovered three aliens inside the trunk.314 The driver,
Ortiz, argued that the search of his car violated the Fourth Amendment.315 The government
asserted that probable cause was not needed to search a vehicle at an immigration checkpoint
because the Border Patrol agent’s discretion in deciding which cars to search was limited by the
location of the checkpoint.316 The government also claimed that a checkpoint stop is less intrusive
than roving patrol stops.317
The Supreme Court determined that the routine nature of a checkpoint stop “does not mitigate the
invasion of privacy that a search entails.”318 The Court also observed that Border Patrol agents
have virtually unlimited discretion whether to search a vehicle at a checkpoint.319 The Court
stated that “[t]his degree of discretion to search private automobiles is not consistent with the
Fourth Amendment,” and “[a] search, even of an automobile, is a substantial invasion of
privacy.”320 Thus, citing Almeida-Sanchez, the Court held that “at traffic checkpoints removed
from the border and its functional equivalents, officers may not search private vehicles without
consent or probable cause.”321 The Court held that the agents’ search of Ortiz’s vehicle was

decision that must be left largely within the discretion of the Border Patrol.” Id. at 562 n.15. The motorists in Martinez-
Fuerte had challenged one of the checkpoint locations (San Clemente), but the Court determined that it was reasonable
given the high number of alien apprehensions in the area, and the fact that the checkpoint was in an area between San
Diego and Los Angeles where traffic was relatively light. Id.
310 Id. at 563.
311 Id. at 563–64.
312 Id. at 567. See also Mich. Dep’t of State Police v. Sitz, 496 U.S. 444, 451–53 (1990) (holding that state’s highway
sobriety checkpoint program, in which all passing vehicles are stopped to determine if the drivers are intoxicated, did
not violate the Fourth Amendment); Delaware v. Prouse, 440 U.S. 648, 663 (1979) (suggesting that police officers
may, without articulable suspicion, use roadblocks to conduct “spot checks” and question all oncoming traffic).
313 United States v. Ortiz, 422 U.S. 891, 892 (1975).
314 Id. at 891–92.
315 Id. at 892.
316 Id. at 894.
317 Id.
318 Id.
319 Id. at 895–96.
320 Id. at 896.
321 Id. at 896–97. The Court noted that not every aspect of a vehicle inspection at a checkpoint (e.g., looking beneath
the chassis) is a “search” for purposes of the Fourth Amendment. Id. at 897 n.3. But the Court declined to specify the
exact scope of an automobile “search.” Id. The Court also cautioned that probable cause is not necessarily required for
all vehicle inspections, and that potentially “different considerations would apply to routine safety inspections required
as a condition of road use.” Id. With regard to establishing probable cause, the Court stated that Border Patrol officers
may consider various factors, including the number of persons in the vehicle; the appearance and behavior of the driver
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unconstitutional because they lacked probable cause that it contained unlawfully present
aliens.322As Ortiz reflects, while Border Patrol agents have broad authority to conduct
suspicionless checkpoint stops for brief questioning, there are constitutional constraints on the
agents’ ability to engage in more intrusive actions at those checkpoints.
Lower Court Decisions on Immigration Checkpoints
Lower courts have also addressed legal challenges to immigration checkpoint stops, including
temporary checkpoints. Generally, courts have recognized the Border Patrol’s authority to briefly
detain and question motorists about citizenship or immigration status without a warrant or
individualized suspicion of unlawful activity.323 Some courts have also held that Border Patrol
agents may ask about the driver’s vehicle (e.g., ownership, number of occupants), travel plans,
and any “suspicious circumstances.”324 Courts have extended agents’ authority to visual
inspections of the vehicle (including the undercarriage),325 requesting immigration-related

and passengers; their inability to speak English; the responses the driver and passengers give to the officers’ questions;
the nature of the vehicle; and indications that the vehicle may be heavily loaded. Id. at 897. Additionally, the officers
may draw “reasonable inferences” from those facts based on their knowledge and prior experience. Id.
322 Id. at 897–98.
323 See, e.g., United States v. Tello, 924 F.3d 782, 786 (5th Cir. 2019) (“At a fixed checkpoint, however, which has as
its primary purpose identifying illegal immigrants, vehicles may be briefly detained in furtherance of that purpose, and
the occupants questioned, without either a warrant or any individualized reasonable suspicion.”) (citing United States v.
Jaime, 473 F.3d 178, 181 (5th Cir. 2006)); United States v. Forbes, 528 F.3d 1273 (10th Cir. 2008) (“[O]ur
jurisprudence holds that ‘border patrol agents may stop, briefly detain, and question individuals [at permanent border
checkpoints] without any individualized suspicion that the individuals are engaged in criminal activity.’ ”) (quoting
United States v. Massie, 65 F.3d 843, 847 (10th Cir. 1995)) (alteration in original); United States v. Machuca-Barrera,
261 F.3d 425, 435 (5th Cir. 2001) (holding that checkpoint stop was permissible where agent asked only a few
questions about immigration status and the stop lasted for no more than a few minutes); United States v. Soto-
Camacho, 58 F.3d 408, 411 (9th Cir. 1995) (“[A] stop conducted at a clearly visible temporary checkpoint pursuant to a
routine inspection of all vehicles for illegal aliens is not unreasonable under the Fourth Amendment.”).
324 See Tello, 924 F.3d at 787 (“As we have stated, ‘questions about travel including origin and destination would be
commonplace for an agent to ask during an immigration inspection.’ ”) (quoting United States v. Alvarez, 750 F. App’x
311, 313 (5th Cir. 2018)); United States v. Rascon-Ortiz, 994 F.2d 749, 752 (10th Cir. 1993) (“[A] few brief questions
concerning such things as vehicle ownership, cargo, destination, and travel plans may be appropriate if reasonably
related to the agent’s duty to prevent the unauthorized entry of individuals into this country and to prevent the
smuggling of contraband.”); United States v. Preciado, 966 F.2d 596, 598 (10th Cir. 1992) (“This court has held that
border patrol agents may question individuals regarding suspicious circumstances, in addition to citizenship matters,
when those individuals are stopped at permanent checkpoints.”) (citing United States v. Benitez, 899 F.2d 995, 998
(10th Cir. 1990)). The Tenth Circuit has stated that “[w]hile there is no single definition of what constitutes a
‘suspicious circumstance,’ border patrol agents are given deference in relying upon their law enforcement training and
past experience in deciding whether a suspicious circumstances exists.” Rascon-Ortiz, 994 F.2d at 753 (citing United
States v. Sanders, 937 F.2d 1495, 1500 (10th Cir. 1991)). Thus, for instance, the court has determined that an agent’s
observation that a motorist’s hands were shaking nervously constituted suspicious circumstances. Id.; see also id. at
753 n.6 (stating that “suspicious circumstances” is not equivalent to the reasonable suspicion standard).
325 See United States v. Gonzalez-Acosta, 989 F.2d 384, 388 (10th Cir. 1993) (“[W]e conclude the undercarriage
inspection of defendant’s vehicle did not constitute a ‘search’ within the meaning of the Fourth Amendment.”); United
States v. Price, 869 F.2d 801, 804 (5th Cir. 1989) (“Because the items observed were in plain view, the visual
inspection was not a search within the meaning of the Fourth Amendment.”); United States v. White, 766 F.2d 1328,
1329 (9th Cir. 1985) (noting that “the Supreme Court approved routine stops for brief questioning and visual inspection
of vehicles”) (citing United States v. Martinez-Fuerte, 428 U.S. 543, 562 n.15 (1976)).
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documents,326 and secondary inspection referrals for further questioning.327 Additionally, agents at
checkpoints may conduct exterior “canine sniffs” of vehicles so long as they do not unreasonably
prolong the checkpoint stop.328 Agents at checkpoints may also board commercial buses, question
the passengers, and inspect the bathrooms, open spaces, and exterior luggage compartments, so
long as the inspection is brief.329
In short, the checkpoint stop must be limited to the time reasonably necessary to determine the
immigration or citizenship status of those passing through the checkpoint.330 For that reason,
lower courts have held that checkpoint stops exceeding the scope of a routine immigration
inspection require at least reasonable suspicion that unlawful activity is afoot.331 In some cases,
checkpoint stops that went beyond a routine inspection were ruled unconstitutional.332

326 See United States v. Garcia-Garcia, 319 F.3d 726, 731 (5th Cir. 2003) (“[Ag]ents at a fixed checkpoint may only
question the passengers briefly (and request documentation) about their immigration status absent reasonable suspicion
of illegal activity that arises before the immigration status of the passengers has been verified.”); Massie, 65 F.3d
at 847–48 (“During a routine fixed-checkpoint stop, border patrol agents may question individuals in the absence of
individualized suspicion about their citizenship and immigration status and request documentation.”); United States v.
Preciado-Robles, 964 F.2d 882, 884 (9th Cir. 1992) (observing that a routine checkpoint stop includes “the production
of immigration documents”).
327 See United States v. Chacon, 330 F.3d 323, 326 (5th Cir. 2003) (“Referral of vehicles to a secondary inspection area
is also permissible under the Fourth Amendment, even in the absence of any individualized suspicion.”) (citations
omitted); United States v. Soyland, 3 F.3d 1312, 1314 (9th Cir. 1993) (observing that “reasonable suspicion is not
necessary” for a referral to secondary inspection); United States v. Maestas, 2 F.3d 1485, 1495 (10th Cir. 1993) (“In
short, Border patrol agents may stop any car at the fixed border checkpoint, and may refer any car for secondary
inspection.”) (emphasis in original).
328 See Tello, 924 F.3d at 787 (“Border Patrol agents may conduct a canine sniff to search for drugs or concealed aliens
at immigration checkpoints so long as the sniff does not lengthen the stop beyond the time necessary to verify the
immigration status of a vehicle’s passengers.”) (citing United States v. Ventura, 447 F.3d 375, 378 (5th Cir. 2006));
Forbes, 528 F.3d at 1277 (“At the border, canine inspections are permissible even in the absence of individualized
suspicion and even without the consent of the vehicle’s driver or occupants.”) (citing Massie, 65 F.3d at 848); United
States v. Taylor, 934 F.2d 218, 221 (9th Cir. 1991) (concluding that a dog sniff at an immigration checkpoint “did not
exceed the boundaries of reasonableness”). A canine alert to a vehicle produces probable cause to search the interior of
that vehicle. United States v. Thomas, 726 F.3d 1086, 1096 (9th Cir. 2013); Forbes, 528 F.3d at 1277; United States v.
Williams, 69 F.3d 27, 28 (5th Cir. 1995).
329 See Ventura, 447 F.3d at 380–81 (“We perceive no constitutional violation in the routine brief inspections of a bus’s
restrooms and undercarriage luggage bins for concealed aliens, so long as such sweeps do not unduly prolong the
checkpoint stop. To hold otherwise would encourage illegal aliens and alien smugglers to conceal themselves and
others in luggage, luggage compartments, engine compartments, and other unsafe places in commercial buses in an
effort to circumvent the checkpoint inspection.”); United States v. Hernandez, 7 F.3d 944, 946 (10th Cir. 1993) (“When
a bus enters the checkpoint and is referred to the secondary inspection location, border patrol agents are permitted to
board the bus, question its passengers regarding citizenship and immigration status, make a brief visual inspection of
their surroundings, and question the passengers regarding suspicious circumstances.”); cf. Florida v. Bostick, 501 U.S.
429, 434–36 (1991) (holding that the police can board a bus and ask passengers questions without reasonable
suspicion).
330 See United States v. Machuca-Barrera, 261 F.3d 425, 433 (5th Cir. 2001) (“The permissible duration of the stop is
limited to the time reasonably necessary to complete a brief investigation of the matter within the scope of the stop.”).
331 See id. at 434 (“[I]f the initial, routine questioning generates reasonable suspicion of other criminal activity, the stop
may be lengthened to accommodate its new justification.”); United States v. Rascon-Ortiz, 994 F.2d 749, 753 (10th Cir.
1993) (“Border Patrol Agents must limit their inspection to a routine checkpoint stop unless consent, probable cause or
reasonable suspicion arises during the stop.”).
332 See, e.g., United States v. Ellis, 330 F.3d 677, 680–81 (5th Cir. 2003) (holding that Border Patrol agent
impermissibly extended detention of bus passengers by “squeezing and sniffing” their baggage for drugs without
reasonable suspicion); United States v. Portillo-Aguirre, 311 F.3d 647, 656–58 (5th Cir. 2002) (ruling that agent who
had completed routine immigration inspection of a bus unlawfully extended the detention by investigating, without
reasonable suspicion, whether a passenger aboard was carrying drugs); United States v. Jackson, 825 F.2d 853, 854
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Transportation Checks
Apart from stopping vehicles at fixed highway checkpoints, the Border Patrol sometimes
conducts “transportation checks” in certain areas near the border, such as bus and train stations.333
During these checks, Border Patrol agents board buses, trains, or other conveyances and ask
passengers about immigration status, travel plans, and luggage.334 The agents may also request
consent to search a passenger or his or her luggage.335 As authority for these transportation
checks, the Border Patrol cites INA Section 287, which authorizes immigration officers to search
vehicles within a reasonable distance of the border and interrogate individuals about immigration
status.336 The Border Patrol argues that trafficking activity at transportation hubs warrants the use
of transportation checks.337
The Supreme Court has not addressed the constitutionality of Border Patrol transportation checks
under the Fourth Amendment. But in Florida v. Bostick, the Court considered whether police
officers engaged in drug interdiction may board buses at scheduled stops, question passengers,
and ask permission to search their luggage.338 Observing that law enforcement officers generally
do not violate the Fourth Amendment by asking people questions on the street or in public
places,339 the Court determined that bus encounters were permissible so long as a reasonable
person “would feel free to decline the officers’ requests or otherwise terminate the encounter.”340
Then, in United States v. Drayton, the Supreme Court reaffirmed the principle that the police
generally may board buses to ask questions, ask for identification, and request consent to search
luggage.341 The Court also held that the police need not inform passengers of their right not to
cooperate and to refuse to consent to a search.342 Citing Bostick, some lower courts have ruled
that Border Patrol agents engaged in transportation checks lawfully boarded buses and questioned
passengers without a warrant or any suspicion of unlawful activity.343 Drayton would appear to

(5th Cir. 1987) (holding that “plenary searches” at permanent checkpoint were unreasonable under the Fourth
Amendment); United States v. Maxwell, 565 F.2d 596, 596–98 (9th Cir. 1977) (holding that checkpoint violated the
Fourth Amendment because it was in a remote area with no buildings or houses nearby, it was marked only by small
stop signs and traffic cones, and it imposed a “sudden, unexpected, and somewhat traumatic” intrusion); United States
v. Summers, 153 F. Supp. 3d 1261, 1267–70 (S.D. Cal. 2015) (ruling that search of automobile trunk at checkpoint
violated the Fourth Amendment because there was no consent or probable cause for the search).
333 U.S. Customs & Border Prot., U.S. Border Patrol Transportation Check Operations (May 11, 2018),
https://www.cbp.gov/document/publications/us-border-patrol-transportation-check-operations.
334 Id.
335 Id.
336 Id.; see 8 U.S.C. § 1357(a)(1), (3).
337 U.S. Customs & Border Prot., U.S. Border Patrol Transportation Check Operations (May 11, 2018),
https://www.cbp.gov/document/publications/us-border-patrol-transportation-check-operations.
338 Florida v. Bostick, 501 U.S. 429, 431 (1991).
339 Id. at 434 (citing California v. Hodari D., 499 U.S. 621, 628 (1991); Florida v. Rodriguez, 469 U.S. 1, 5–6 (1984);
INS v. Delgado, 466 U.S. 210, 216 (1984); Florida v. Royer, 460 U.S. 491, 497 (1983); United States v. Mendenhall,
446 U.S. 544, 557–58 (1980)).
340 Id. at 436. The Court rejected the contention that a police encounter on a bus is more intimidating than other public
encounters because a reasonable person would not feel free to leave a bus that is scheduled to depart. Id. at 435–36. The
Court reasoned that, when freedom of movement is “restricted by a factor independent of police conduct” (e.g., being a
passenger on a bus), the appropriate inquiry is not whether a reasonable person would feel free to leave, but whether
such person would feel free to decline the officers’ requests or otherwise terminate the encounter. Id. at 436.
341 United States v. Drayton, 536 U.S. 194, 203–04 (2002).
342 Id. at 206–07.
343 See, e.g., United States v. Angulo-Guerrero, 328 F.3d 449, 451 (8th Cir. 2003) (holding that a bus passenger was not
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lend further support to these holdings. Even so, some argue that the Border Patrol’s practice of
boarding buses, trains, or other forms of transportation is intimidating and coercive and may
infringe upon those passengers constitutional rights.344 In 2020, Greyhound, the largest bus
company in the United States, announced it would no longer allow Border Patrol agents to board
its buses away from checkpoints or enter nonpublic areas of its terminals without its consent or a
warrant.345 DHS updated its boarding policy by requiring Border Patrol agents to gain access to
the bus with the consent of the company’s owner or one of the company’s employees.346
Select Legal Issues
The federal government has broad authority to conduct warrantless searches and seizures at the
border or its functional equivalent, but that authority is not unfettered. The government’s
authority is generally limited to routine border searches, such as the inspection of luggage and
containers.347 “Highly intrusive” border searches may require at least reasonable suspicion of a
crime.348 In recent years, lower courts have considered whether searches of electronic devices
(e.g., cell phones) exceed a routine border search given the amount of private information that
might be stored within them. And DHS’s increased use of drone surveillance and biometric
collection at the border has also prompted debate over whether these activities should receive
greater constitutional scrutiny and, even if constitutionally permissible, whether there should be
more statutory limitations on their use. Apart from the government’s ability to conduct these
types of searches at the border, there has also been some debate about the prevalence and
lawfulness of “racial profiling” by law enforcement when making investigatory stops near the
border. This section explores these legal issues.
Border Searches of Electronic Devices
The Supreme Court has not yet addressed whether the Fourth Amendment’s border search
exception extends to warrantless searches of electronic devices such as cell phones and
computers—devices that may contain more personal and sensitive information than typically
found in a briefcase or automobile. Lower courts have addressed the constitutionality of border
searches of electronic devices in a few notable cases. To date, lower courts have generally held

subject to a Fourth Amendment seizure when he answered Border Patrol agent’s questions on the bus); United States v.
Gonzales, 979 F.2d 711, 713–14 (9th Cir. 1992) (holding that a “routine bus sweep” by Border Patrol agents was
permissible under the Fourth Amendment); United States v. Mendieta-Garza, 254 F. App’x 307 (5th Cir. Nov. 9, 2007),
2007 WL 3340822, at *5–6 (concluding that no seizure occurred where Border Patrol agents boarded bus without
making any intimidating movements or show of force); United States v. Montano, No. B-11-482, 2011 WL 13157358,
at *3 (S.D. Tex. Sept. 14, 2011) (“As Florida v. Bostick made clear, a law enforcement officer is allowed to approach
any individual and ask questions. That case dealt with an officer’s questioning of bus passengers when they were
already on the bus, which was permissible.”).
344 See Letter from Jennie Pasquarella, Dir. of Immigrants’ Rights, ACLU Founds. of Cal. et al. to David Leach, Pres.
& CEO of Greyhound Lines, Inc., Re: Immigration Raids on Greyhound Buses (Mar. 21, 2018),
https://www.aclumaine.org/sites/default/files/aclu_affiliate_letter_to_greyhound_-_final.pdf (contending that CBP’s
bus boarding practices “often evince a blatant disregard for passengers’ constitutional rights” and providing illustrative
examples where passengers were purportedly harassed and intimidated).
345 See Gene Johnson, Greyhound to Stop Allowing Immigration Checks on Buses, ASSOCIATED PRESS (Feb. 21, 2020),
https://apnews.com/dc560c3581783c746aee1544c8ad1c85.
346 See Gene Johnson, AP Exclusive: Agency Memo Contradicts Greyhound on Bus Raids, ASSOCIATED PRESS (Feb. 14,
2020), https://apnews.com/48960c783dd3f22af2ad320227e40b20.
347 See supra “Routine Searches and Seizures.”
348 See Flores-Montano, 541 U.S. at 152.
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that federal officers may conduct relatively limited, manual searches of such devices without a
warrant or any individualized suspicion of unlawful activity, but have disagreed as to whether
more intrusive searches require heightened suspicion.
Riley v. California
In the 2014 decision Riley v. California, the Supreme Court considered the constitutionality of
warrantless electronic device searches in the interior of the United States.349 The Court held that
the police may not conduct a warrantless search of a cell phone seized during an arrest, even
though the Fourth Amendment’s warrant requirement usually does not apply to searches incident
to a lawful arrest.350 Noting that this exception ordinarily applies to brief physical searches of
property within the immediate control of the arrestee to prevent potential harm to the police
officers and the destruction of evidence, the Court determined that “[t]here are no comparable
risks when the search is of digital data.”351
The Riley Court also concluded that searching cell phone data raises greater privacy concerns
than searching physical items typically found on a person, such as a wallet.352 The Court observed
that cell phones—unlike most other physical items—carry “immense storage capacity” and a
broader range of private information, including photographs, videos, contact information, text
messages, financial records, and internet browsing history.353 For that reason, “[c]ell phones differ
in both a quantitative and a qualitative sense from other objects that might be kept on an
arrestee’s person.”354 The Court thus held that the police must secure a warrant before searching
the contents of a cell phone seized during an arrest,355 but it noted that “other case-specific
exceptions may still justify a warrantless search of a particular phone.”356 The Court did not
address whether the border search exception permits warrantless electronic device searches at the
border.
Lower Courts’ Application of the Border Search Exception to Electronic Device
Searches
Lower courts have applied the border search exception to electronic device searches. For
instance, in United States v. Ickes, the Fourth Circuit held that manually inspecting the contents of
a computer and disks at the border was permissible given “the Supreme Court’s insistence that
U.S. officials be given broad authority to conduct border searches.”357 In United States v. Arnold,
the Ninth Circuit similarly ruled that the search of a computer fell within the border search

349 Riley v. California, 573 U.S. 373, 378, 385 (2014).
350 Id. at 401 (“[A] warrant is generally required before such a search, even when a cell phone is seized incident to
arrest.”).
351 Id. at 386.
352 Id. at 393.
353 Id. at 393–94.
354 Id. at 393.
355 Id. at 403.
356 Id. at 401–02. The Court suggested, for example, that searching a cell phone without a warrant might be warranted
in exigent circumstances to prevent the imminent destruction of evidence, to pursue a fleeing suspect, or to assist those
who are seriously injured or threatened with imminent injury. Id. at 402.
357 United States v. Ickes, 393 F.3d 501, 506 (4th Cir. 2005).
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exception because examining a computer’s files is analogous to scanning the contents of
luggage.358
Courts have disagreed on whether more intrusive border searches of electronic devices require
particularized suspicion of criminal activity. In United States v. Cotterman, the Ninth Circuit held
that, while a “quick look” at computer files would not require any particularized suspicion, a
forensic examination of the hard drive (i.e., using software to copy the hard drive and analyze its
contents, including deleted content) exceeded a routine border search given its “comprehensive
and intrusive nature.”359 The court held that the forensic examination—which it described as a
“computer strip search”—required reasonable suspicion.360 In United States v. Kolsuz, the Fourth
Circuit ruled that the forensic border analysis of a cell phone required “some form of
individualized suspicion” given the exposure of “uniquely sensitive information” within the
device.361 Citing Riley, the court reasoned that cell phones are “fundamentally different” from
objects traditionally subject to government searches, such as wallets and bags.362
Conversely, in United States v. Touset, the Eleventh Circuit held that the Fourth Amendment
requires no suspicion of unlawful activity for forensic border searches of electronic devices.363
The court observed that, although the Supreme Court has required reasonable suspicion for highly
intrusive border searches of a person’s body (e.g., a rectal examination), the Court has never
extended this requirement to border searches of property “however nonroutine and intrusive.”364
The court also reasoned that Riley’s restrictions on warrantless cell phone searches incident to an
arrest did not apply to searches at the border, where there are diminished privacy expectations.365
Courts have also disagreed about the proper scope of an electronic device search at the border. In
United States v. Cano, the Ninth Circuit held that an electronic device search must be limited to a
search for digital contraband within the device itself (e.g., child pornography), and does not
encompass searching the device for any evidence that may lead to the discovery of a crime.366
Thus, the court determined, border officials may conduct a forensic search of a cell phone only if

358 United States v. Arnold, 533 F.3d 1003, 1008–10 (9th Cir. 2008).
359 United States v. Cotterman, 709 F.3d 952, 960, 966 (9th Cir. 2013). The court explained that “[e]lectronic devices
often retain sensitive and confidential information far beyond the perceived point of erasure, notably in the form of
browsing histories and records of deleted files.” Id. at 965. According to the court, “[s]uch a thorough and detailed
search of the most intimate details of one’s life is a substantial intrusion upon personal privacy and dignity.” Id. at 968.
360 Id. at 966, 968; see also United States v. Cano, 934 F.3d 1002, 1016 (9th Cir. 2019), reh’g denied, 973 F.3d 966
(9th Cir. 2020) (holding that recording of phone numbers and text messages from cell phone for further processing
exceeded routine border search and required reasonable suspicion).
361 United States v. Kolsuz, 890 F.3d 133, 145–46 (4th Cir. 2018).
362 Id. See also United States v. Saboonchi, 990 F. Supp. 2d 536, 561 (D. Md. 2014) (“It is the potentially limitless
duration and scope of a forensic search of the imaged contents of a digital device that distinguishes it from a
conventional computer search. The latter may take hours and delve deeply into the contents of the device, but it is
difficult to conceive of a conventional search of a computer or similar device at a border lasting days or weeks.”).
363 United States. v. Touset, 890 F.3d 1227, 1233 (11th Cir. 2018). The court noted, for example, that the Supreme
Court has upheld the suspicionless search of a fuel tank at the border, without imposing heightened requirements for
other types of personal property. Id. (citing United States v. Flores-Montano, 541 U.S. 149, 155 (2004)).
364 Id.
365 Id. at 1234. See also United States v. Vergara, 884 F.3d 1309, 1312 (11th Cir. 2018) (observing that, in Riley, the
Supreme Court “expressly limited its holding to the search-incident-to-arrest exception,” and recognized that other
exceptions may justify a warrantless search of a cell phone).
366 United States v. Cano, 934 F.3d 1002, 1018–19 (9th Cir. 2019), reh’g denied, 973 F.3d 966 (9th Cir. 2020)
(“[B]order officials are limited to searching for contraband only; they may not search in a manner untethered to the
search for contraband.”). The court distinguished searches of items that are actually being smuggled from searches of
evidence that may reveal the importation of contraband. Id. at 1018.
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there is reasonable suspicion that it physically contains contraband.367 In United States v.
Aigbekaen, the Fourth Circuit ruled that CBP officials may conduct a forensic border search of an
electronic device so long as there is reasonable suspicion that it contains evidence of a crime that
“bears some nexus” to the justifications for the border search exception (e.g., to protect national
security, to block entry of unwanted persons, to exclude contraband).368 In Alasaad v. Mayorkas,
the First Circuit held that “advanced border searches of electronic devices may be used to search
for contraband, evidence of contraband, or for evidence of activity in violation of the laws
enforced or administered by CBP or ICE.”369
In sum, lower courts have generally agreed that CBP officers may conduct relatively limited,
manual searches of electronic devices at the border without a warrant or any particularized
suspicion. But courts have disagreed about whether more intrusive, forensic searches require at
least reasonable suspicion of a crime, and whether that reasonable suspicion must be tied to
evidence of contraband within the device itself, or any evidence of potential criminal activity that
may be taking place.370
Current CBP Policies on Electronic Device Searches
As courts have considered whether electronic device searches fit within the border search
exception, CBP has developed policies governing border searches of electronic devices.371
Currently, the agency permits “basic” manual searches of electronic devices “with or without
suspicion” of criminal activity, but restricts “advanced” forensic searches to cases where there is
reasonable suspicion or a “national security concern.”372 CBP also permits officers to “detain” an
electronic device (or copies of information from it) “for a brief, reasonable period of time to
perform a more thorough border search,” generally not exceeding a period of five days.373 CBP

367 Id. at 1020.
368 United States v. Aigbekaen, 943 F.3d 713, 721 (4th Cir. 2019). Thus, the court held that the warrantless forensic
search of an airplane passenger’s laptop computer, cell phone, and digital media player based on suspicion that he was
involved in domestic sex trafficking of minors did not fall within the border search exception because the search
“lacked the requisite nexus to the recognized historic rationales justifying the border search exception.” Id.
369 Alasaad v. Mayorkas, 988 F.3d 8, 21 (1st Cir. 2021).
370 While some courts have considered whether CBP officials must have reasonable suspicion to conduct warrantless
forensic searches of electronic devices at the border, other courts have declined to reach that question, instead
concluding that the evidence from a challenged forensic search need not be suppressed because the officers acted on a
good faith, reasonable belief they could conduct the warrantless search. See, e.g., United States v. Aguilar, 973 F.3d
445, 449–50 (5th Cir. 2020) (“Given the state of the law at the time Aguilar’s phone was forensically searched, we
conclude that the border agents had a good faith, reasonable belief that they could search Aguilar’s phone without
obtaining a warrant.”); United States v. Wanjiku, 919 F.3d 472, 485–86 (7th Cir. 2019) (“Given the state of the law at
the time of these searches of the contents of Wanjiku’s electronic devices, the agents therefore possessed an objectively
good faith belief that their conduct did not violate the Fourth Amendment because they had reasonable suspicion to
conduct the searches.”).
371 The agency defines an “electronic device” to include “any device that may contain information in an electronic or
digital form, such as computers, tablets, disks, drives, tapes, mobile phones and other communication devices, cameras,
music and other media players.” U.S. Customs & Border Prot., Subject: Border Search of Electronic Devices ¶ 3.2
(Jan. 4, 2018), https://www.dhs.gov/sites/default/files/publications/CBP%20Directive%203340-049A_Border-Search-
of-Electronic-Media.pdf.
372 See id. ¶¶ 5.1.3, 5.1.4. According to CBP, an “advanced search” occurs when an immigration officer “connects
external equipment, through a wired or wireless connection, to an electronic device not merely to gain access to the
device, but to review, copy, and/or analyze its contents.” Id. ¶ 5.1.4. The agency describes a “basic search” simply as
any electronic device search that is “not an advanced search” (i.e., manually examining the device and reviewing its
contents). Id. ¶ 5.1.3.
373 Id. ¶ 5.4.1.
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officers may also “seize and retain” the device (or copies of information from the device) if there
is probable cause that the device contains evidence of a crime.374
CBP’s distinctions between “basic” and “advanced” electronic device searches mirror the Fourth
and Ninth Circuits’ differing standards between manual and forensic border searches of electronic
devices. In contrast, a federal district court in Massachusetts held that any noncursory border
search of an electronic device—whether basic or advanced—requires reasonable suspicion
because both types of searches can access “a wealth of personal information.”375 But the First
Circuit in Alasaad v. Mayorkas partially reversed that decision, holding that the privacy concerns
implicated by a basic, manual search are “tempered by the fact that the searches are taking place
at the border,” where there is a heightened interest in preventing the entry of unwanted persons
and goods.376 The court also observed that a basic search does not involve an intrusive search of a
person, and is limited to accessing information on the device itself.377 The court thus held that a
basic electronic device search at the border is a routine search requiring no reasonable
suspicion.378
Therefore, given the government’s broad authority to conduct routine searches at the border
without a warrant or any suspicion of unlawful activity, lower courts have agreed that the
government’s authority extends to relatively limited, manual border searches of electronic
devices, such as cell phones and computers. But there is some disagreement among lower courts
over how that authority extends to forensic border searches of electronic devices.
Drone Surveillance
The Homeland Security Act of 2002 establishes an Air and Marine Operations (AMO) unit within
CBP, and authorizes the agency to conduct unmanned aerial operations.379 Additionally, the
Intelligence Reform and Terrorism Prevention Act of 2004 requires DHS to implement remote

374 Id. ¶ 5.5.1.1. ICE, the DHS component primarily responsible for immigration enforcement in the interior of the
United States, as well as the investigation of cross-border criminal activity, may also play a role. For example, when
CBP seizes or detains an electronic device, it may turn over the device to ICE for analysis and investigation. Id. ¶ 2.7.
Under current ICE policy, a “basic search” of an electronic device does not require any suspicion of criminal activity,
while an “advanced search” requires reasonable suspicion. See Alasaad v. Nielsen, 419 F. Supp. 3d 142, 148 (D. Mass.
2019), rev’d on other grounds, 988 F.3d 8 (1st Cir. 2021).
375 See Alasaad, 419 F. Supp. 3d at 163 ̶ 65. The court reasoned that “even a basic search allows for both a general
perusal and a particularized search of a traveler’s personal data, images, files and even sensitive information.” Id. at
163. The court distinguished a basic search from a cursory search confined to “a brief look reserved to determining
whether a device is owned by the person carrying it across the border, confirming that it is operational and that it
contains data.” Id.
376 Alasaad v. Mayorkas, 988 F.3d 8, 18 (1st Cir. 2021).
377 Id. at 18 ̶ 19.
378 Id. at 19. The First Circuit left undisturbed the district court’s ruling that advanced searches require reasonable
suspicion; but, as noted, both CBP and ICE policies currently require reasonable suspicion for such searches. See U.S.
Customs & Border Prot., Subject: Border Search of Electronic Devices ¶ 5.1.4 (Jan. 4, 2018),
https://www.cbp.gov/sites/default/files/assets/documents/2018-Jan/CBP-Directive-3340-049A-Border-Search-of-
Electronic-Media-Compliant.pdf.
379 Trade Facilitation and Trade Enforcement Act of 2015, Pub. L. No. 114-125, § 802, 130 Stat. 122 (2016) (amending
Homeland Security Act of 2002, Pub. L. No. 107-296, § 411, 116 Stat. 2135 (2002)) (codified at 6 U.S.C. § 211(f)(3),
(4), (k)).
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aerial surveillance programs along the southwest border.380 Annual appropriations legislation also
funds and authorizes CBP operations, including remote aerial surveillance.381
Based on this authority, CBP’s AMO uses helicopters, fixed-wing aircraft, and unmanned aircraft
systems to conduct surveillance within the border region, including to intercept drug smugglers
and illegal border crossers.382 In particular, the agency uses “Predator B” drones that record high-
quality videos and collect data from the ground with long-range cameras, radio transmitters, and
infrared sensors.383 The drones can identify and track persons and vehicles on the ground, as well
as detect physical objects such as backpacks, signs, firearms, and license plates.384
In recent years, some lawmakers and commenters have expressed concern that drone surveillance
might raise privacy concerns.385 These concerns have mainly focused on the use of drone
surveillance for domestic law enforcement purposes.386 There may be instances where the
distinction between border-related drone surveillance and domestic surveillance may be blurred.
A significant portion of the U.S. populace lives near the border,387 and CBP sometimes shares
information collected through border drone surveillance with state and local entities for law
enforcement purposes.388
That said, reviewing courts may view constitutional challenges to drone surveillance at the border
with skepticism. The Supreme Court has rejected Fourth Amendment challenges to warrantless

380 Intelligence Reform and Terrorism Prevention Act of 2004, Pub. L. No. 108-458, § 5201(a), (c), 118 Stat. 3638
(2004).
381 See Consolidated Appropriations Act of 2020, Pub. L. No. 116-93, Tit. II, 133 Stat. 2317, 2506 (2019); Continuing
Appropriations Act, 2021, and Other Extensions Act, Pub. L. No. 116-159, Div. A, § 101(6), 134 Stat. 709, 710 (2020).
382 See U.S. Customs & Border Prot., Air and Marine Operations Assets (Jan. 9, 2020), https://www.cbp.gov/border-
security/air-sea/aircraft-and-marine-vessels. See also U.S. Customs & Border Prot., Air and Marine Operations (2018),
https://www.cbp.gov/sites/default/files/assets/documents/2017-Dec/FS_2018_AMO_Fact%20Sheet.pdf (“AMO
interdicts unlawful people and cargo approaching U.S. borders, investigates criminal networks and provides domain
awareness in the air and maritime environments, and responds to contingencies and national taskings.”).
383 See Sidney Fussel, The Endless Aerial Surveillance of the Border, ATLANTIC (Oct. 11, 2019),
https://www.theatlantic.com/technology/archive/2019/10/increase-drones-used-border-surveillance/599077/; David
Bier & Matthew Feeney, Drones on the Border: Efficacy and Privacy Implications, CATO INST. (May 1, 2018),
https://www.cato.org/publications/immigration-research-policy-brief/drones-border-efficacy-privacy-implications.
384 Id.
385 See, e.g., Letter from Reps. Anna Eshoo & Bobby Rush to Christopher Wray, Dir., FBI et al. (June 9, 2020)
(arguing that the use of Predator B drones and certain other forms of aerial surveillance to collect information about
protesters constituted “vast overreach of federal government surveillance”); Sen. Ed Markey, Senator Markey & Rep.
Welch Introduce Legislation to Ensure Transparency, Privacy for Drone Use (Mar. 15, 2017),
https://www.markey.senate.gov/news/press-releases/-senator-markey-and-rep-welch-introduce-legislation-to-ensure-
transparency-privacy-for-drone-use (“ ‘Drones flying overhead could collect very sensitive and personally identifiable
information about millions of Americans, but right now, we don’t have sufficient safeguards in place to protect our
privacy’ said Senator Markey, a member of the Commerce, Science and Transportation Committee.”); Rebecca L.
Scharf, Game of Drones: Rolling the Dice With Unmanned Aerial Vehicles and Privacy, 2018 UTAH L. REV. 457, 461
(2018) (arguing that “drones are simply not like any other technology and their potential for wreaking havoc on the
fabric of privacy in our society is too great for their use to continue without additional guidelines”).
386 See, e.g., Letter, supra note 385, at 1–2 (describing federal law enforcement agencies’ use of drone and other forms
of aerial surveillance during nationwide protests in American cities).
387 See Tanvi Misra, Inside the Massive U.S. “Border Zone” (May 14, 2018),
https://www.bloomberg.com/news/articles/2018-05-14/mapping-who-lives-in-border-patrol-s-100-mile-zone.
388 See Craig Whitlock & Craig Timberg, Border-Patrol Drones Being Borrowed by Other Agencies More Often than
Previously Thought, WASH. POST (Jan. 14, 2014), https://www.washingtonpost.com/world/national-security/border-
patrol-drones-being-borrowed-by-other-agencies-more-often-than-previously-known/2014/01/14/5f987af0-7d49-11e3-
9556-4a4bf7bcbd84_story.html.
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aerial surveillance of open areas in the interior of the United States, holding that there is no
reasonable expectation of privacy in places visible from the public navigable airspace.389 Citing
Supreme Court precedent, some lower courts have likewise been unpersuaded by Fourth
Amendment challenges to warrantless drone surveillance by domestic law enforcement.390
Because the range of information accessible by the drones’ technology potentially exceeds what
would typically be exposed from an aerial vantage point (e.g., a helicopter), some argue that
remote aerial surveillance should be subject to greater Fourth Amendment scrutiny.391 In recent
years, the Supreme Court has recognized instances when technologically assisted surveillance of
persons’ public activities can intrude upon privacy interests protected by the Fourth
Amendment.392 The Court has indicated that the use of advanced surveillance technology to probe
into “intimate details” may raise constitutional concerns.393 But it is not clear that aerial drone
surveillance would necessarily raise the same issues as other forms of advanced surveillance,
such as thermal imaging, monitoring cell phone locations, or installing a tracking device on a
vehicle.394

389 See Florida v. Riley, 488 U.S. 445, 450–51 (1989) (“Any member of the public could legally have been flying over
Riley’s property in a helicopter at the altitude of 400 feet and could have observed Riley’s greenhouse. The police did
no more.”); Dow Chem. Co. v. United States, 476 U.S. 227, 239 (1986) (“[S]uch an industrial complex is more
comparable to an open field and as such it is open to the view and observation of persons in aircraft lawfully in the
public airspace immediately above or sufficiently near the area for the reach of cameras.”); California v. Ciraolo, 476
U.S. 207, 213–15 (1986) (“In an age where private and commercial flight in the public airways is routine, it is
unreasonable for respondent to expect that his marijuana plants were constitutionally protected from being observed
with the naked eye from an altitude of 1,000 feet.”).
390 See Leaders of a Beautiful Struggle v. Baltimore Police Dep’t, 456 F. Supp. 3d 699, 713 (D. Md.), aff’d, 979 F.3d
219 (4th Cir. 2020), reh’g granted, No. 20-1495 (4th Cir. Dec. 22, 2020) (“Common strands emerge from these aerial
surveillance cases. Chief among these is that the Supreme Court and the Fourth Circuit have generally upheld
warrantless aerial surveillance. Fourth Amendment concerns are unlikely to be implicated so long as the surveillance
occurs within navigable or regularly traveled airspace, and the flight does not permit the visual observation of ‘intimate
details’ associated with a person’s home, or disturb the use of a person’s property by means of ‘wind, dust, or threat of
injury.’ ”) (quoting Riley, 488 U.S. at 451–52, 454 (O’Connor, J., concurring); Ciraolo, 476 U.S. at 215; Dow, 476 U.S.
at 238)); State v. Brossart, No. 32-2011-CR-0049, slip op. at 12 (D.N.D. July 31, 2012) (rejecting claim that the
warrantless use of an unmanned aerial vehicle over criminal defendants’ property in North Dakota during their arrest
violated the Fourth Amendment).
391 See, e.g., Rebecca L. Scharf, Game of Drones: Rolling the Dice With Unmanned Aerial Vehicles and Privacy, 2018
UTAH L. REV. 457, 461 (2018) (arguing that “drones are simply not like any other technology and their potential for
wreaking havoc on the fabric of privacy in our society is too great for their use to continue without additional
guidelines.); Nina Gavrilovic, The All-Seeing Eye in the Sky: Drone Surveillance and the Fourth Amendment, 93 U.
DET. MERCY L. REV. 529, 546 (2016) (“Drones provide a cheap, effective alternative to traditional surveillance and can
covertly collect a vast amount of data incomparable to any singular type of surveillance addressed by Fourth
Amendment case law.”); Shane Crotty, The Aerial Dragnet: A Drone-Ing Need for Fourth Amendment Change, 49
VAL. U. L. REV. 219, 247 (2014) (“Drone technology threatens the protections afforded by the Fourth Amendment by
intruding into an individual's life and tracking every movement while on a public thoroughfare.”); Timothy T.
Takahashi, Ph.D., Drones and Privacy, 14 COLUM. SCI. & TECH. L. REV. 72, 113 (2013) (“Until the Supreme Court
weighs in definitively, advances in miniaturized remote sensing technology will blur the boundaries between
reasonable observation and unreasonable eavesdropping.”).
392 Carpenter v. United States, 138 S. Ct. 2206, 2217 (2018); United States v. Jones, 565 U.S. 400, 404–05 (2012);
United States v. Kyllo, 533 U.S. 27, 34 (2001).
393 Dow Chem. Co., 476 U.S. at 238–39.
394 See Kyllo, 533 U.S. at 34 (“We think that obtaining by sense-enhancing technology any information regarding the
interior of the home that could not otherwise have been obtained without physical ‘intrusion into a constitutionally
protected area’ ” constitutes a search—at least where (as here) the technology in question is not in general public use.”)
(quoting Silverman v. United States, 365 U.S. 505, 512 (1961)); Jones, 565 U.S. at 404 (“We hold that the
Government’s installation of a GPS device on a target’s vehicle, and its use of that device to monitor the vehicle’s
movements, constitutes a ‘search’ . . . within the meaning of the Fourth Amendment when it was adopted.”);
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Some courts have rejected Fourth Amendment challenges to warrantless drone surveillance in the
interior of the United States, citing the Supreme Court’s jurisprudence permitting warrantless
aerial surveillance.395 It would seem that constitutional challenges to border drone surveillance
would face even more significant challenges, given the Court’s recognition that the government
has broader search authority at the border, where its national security interest “is at its zenith.”396
Biometric Data Collection at the Border
Biometric data is frequently collected from international travelers. The term biometric data
generally refers to unique personal identifiers—such as fingerprints, DNA, iris or retinal scan,
voice recording, walking gait, and facial geometry.397 Several federal statutes address the
collection and use of biometric data by government entities. Most of these statutes involve the
screening of arriving or departing international travelers and other border security measures,
rather than the collection of biometric data in the interior of the United States.398 For example, 8
U.S.C. § 1365b requires DHS to establish an integrated, automated biometric entry and exit
system that records the arrival and departure of foreign nationals, collects biometric data of
foreign nationals to verify their identity, and authenticates travel documents through the
comparison of biometrics.399 Another statute, 6 U.S.C. § 1118, requires CBP and the
Transportation Security Administration to consult on the deployment of biometric technologies,
and further requires DHS to assess the impacts of biometric technology use and submit a report to
Congress.400
DHS’s Office of Biometric Identity Management (OBIM) maintains a biometric database called
the Automated Biometric Identification System (IDENT)—holding more than 260 million unique
identifiers—that is used for a variety of purposes, including “to detect and prevent illegal entry
into the United States,” facilitate travel, and the verification of visa applications.401 DHS also

Carpenter, 138 S. Ct. at 2217 (“Whether the Government employs its own surveillance technology as in Jones or
leverages the technology of a wireless carrier, we hold that an individual maintains a legitimate expectation of privacy
in the record of his physical movements as captured through [cell-site location information].”). For instance, in one
case, a federal district court held that a that a police department’s use of remote aerial surveillance to capture imagery
data for the purpose of solving violent crimes was not a search under the Fourth Amendment because it merely showed
individuals as “a series of anonymous dots,” had limited location-tracking capabilities, and lacked the ability to show
bodily movements, record in real time, zoom-in on suspicious activities, or reveal “intimate details” from inside or near
a home. Leaders of a Beautiful Struggle, 456 F. Supp. 3d at 714. The court, in fact, determined that the surveillance “is
far less invasive than the feats of aerial surveillance permitted in Riley, Ciraolo, and Dow.” Id. at 713.
395 See Leaders of a Beautiful Struggle, 456 F. Supp. 3d at 713; State v. Brossart, No. 32-2011-CR-0049, slip op. at 12
(D.N.D. July 31, 2012).
396 United States v. Flores-Montano, 541 U.S. 149, 152 (2004); see also United States v. Montoya de Hernandez, 473
U.S. 531, 539–40 (1985) (“But not only is the expectation of privacy less at the border than in the interior, the Fourth
Amendment balance between the interests of the Government and the privacy right of the individual is also struck more
favorably to the Government at the border.”).
397 Carra Pope, Biometric Data Collection in an Unprotected World: Exploring the Need for Federal Legislation
Protecting Biometric Data, 26 J.L. & POL’Y 769, 773–74 (2018).
398 See, e.g., 8 U.S.C. § 1379 (mandating the Attorney General or the Secretary of State to consult with Congress to
“develop and certify a technology standard, including appropriate biometric identifier standards, that can be used to
verify the identity of persons” applying for a visa or seeking admission using a visa); id. § 1731 (directing the
development of an integrated entry and exit data system); id. § 1732 (calling for machine-readable, tamper-resistant
entry and exit documents).
399 Id. § 1365b.
400 6 U.S.C. § 1118(c).
401 DHS, Biometrics, https://www.dhs.gov/biometrics (last visited Sept. 24, 2020).
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shares biometric information “to support homeland security, defense, and justice missions.”402
DHS is in a multiyear transition to replace IDENT with the Homeland Advanced Recognition
Technology System (HART). That system is to likewise store and process biometric data,
including face images.403
The method of biometrics collection and the kinds of biometric data obtained depend on the
foreign national’s method of entry and immigration status.404 Notably, CBP has, because of
rapidly changing technology, started to adopt other manners of collecting biometric data at
airports, seaports, and land ports of entry—with the most notable being facial recognition
technology.405 CBP has deployed facial recognition technology, known as Traveler Verification
Service (TVS), at air, sea, and land environments.406 CBP is also using facial recognition and iris-
scanning technology for pedestrian travelers at some land ports of entry, as well as facial
recognition of occupants in moving vehicles as they enter and exit the United States.407 In
addition, CBP collects biometric information of persons interdicted when illegally crossing the
international border.408

402 Id.
403 See generally DHS, PRIVACY IMPACT ASSESSMENT FOR THE HOMELAND ADVANCED RECOGNITION TECHNOLOGY
SYSTEM (HART) INCREMENT 1 PIA, DHS/OBIM/PIA-004 (Feb. 24, 2020),
https://www.dhs.gov/sites/default/files/publications/privacy-pia-obim004-hartincrement1-february2020_0.pdf.
404 Ordinarily, an alien seeking entry with a visa must apply for a U.S. visa abroad and supply a digital photograph and
electronic fingerprints during the application process, which is verified upon arrival. Safety and Security of U.S.
Borders: Biometrics, U.S. DEP’T. OF STATE, https://travel.state.gov/content/travel/en/us-visas/visa-information-
resources/border-biometrics.html (last visited June 15, 2020); see also 8 U.S.C. § 1732 (requiring machine-readable,
tamper-resistant entry and exit documents for visa applicants). For many travelers holding a passport from a country
participating in the Visa Waiver Program, this application process is not required, and the foreign national may present
a passport without a visa to visit the United States. For information regarding the Visa Waiver Program (VWP) and to
see a list of participating countries, see CRS Report R46300, Adding Countries to the Visa Waiver Program: Effects on
National Security and Tourism (Apr. 1, 2020). For a country to qualify to participate in the VWP, it must comply with
certain biometric requirements. See id. The participating country must issue electronic, machine-readable passports that
contain a biometric identifier (i.e., e-passports) and certify that it is developing a program to issue tamper-resistant,
machine-readable visa documents that incorporate biometric identifiers that are verifiable at the country’s port of entry.
Id. Then, when seeking admission into the United States, a traveler’s identity is verified using the electronic fingerprint
data and digital photographs. Id. For further information on arrival and departure inspections for travelers entering the
country under the VWP, see CRS Report RL32221, Visa Waiver Program (June 29, 2020). Certain individuals are
exempt from the biometric requirements: Canadian citizens who are not required to present a visa or be issued Form I-
94 or Form I-95 for admission or parole into the United States; aliens younger than 14 or older than 79 on the date of
admission; aliens admitted in certain immigration categories; classes of aliens to whom the Secretary of Homeland
Security and the Security of States jointly determine it shall not apply; or other individual alien to whom the Security of
Homeland Security, the Secretary or States, or the Director of Central Intelligence determines it shall not apply. 8
C.F.R. § 235.1(f)(iv).
405 See, e.g., Test to Collect Facial Images from Occupants in Moving Vehicles at the Anzalduas Port of Entry
(Anzalduas Biometric Test), 83 Fed. Reg. 56,862 (Nov. 14, 2018).
406 DHS, PRIVACY IMPACT ASSESSMENT FOR TRAVELER VERIFICATION SERVICE, DHS/CBP/PIA-056 (Nov. 14, 2018),
https://www.dhs.gov/sites/default/files/publications/privacy-pia-cbp056-tvs-january2020_0.pdf.
407 See, e.g., Agency Information Collection Activities: Biometric Identity, 83 Fed. Reg. 24,326 (Mar. 25, 2018); Test to
Collect Biometric Information at the Otay Mesa Port-of-Entry, 80 Fed. Reg. 70,241 (Nov. 13, 2015); see also Test to
Collect Facial Images from Occupants in Moving Vehicles at the Anzalduas Port of Entry (Anzalduas Biometric Test),
83 Fed. Reg. 56,862 (Nov. 14, 2018).
408 DHS, PRIVACY IMPACT ASSESSMENT FOR THE AUTOMATED BIOMETRIC IDENTIFICATION SYSTEM (IDENT),
DHS/NPPD/PIA-002, at 2-5 (Dec. 7, 2012), (discussing the data shared and stored in DHS’s biometric database
IDENT); DHS, PRIVACY IMPACT ASSESSMENT FOR THE HOMELAND ADVANCED RECOGNITION TECHNOLOGY SYSTEM
(HART) INCREMENT 1 PIA, DHS/OBIM/PIA-004, at 16-17 (Feb. 24, 2020) (identifying data collected and stored in the
HART system that replaces IDENT as DHS’s central biometric database).
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Some have raised privacy concerns over the collection and use of biometric identifiers by DHS.409
Although the Supreme Court has not considered a Fourth Amendment challenge to the collection
of biometric data at the border or its functional equivalent, jurisprudence suggests that minimally
intrusive collection of biometric data at the border does not affront the Fourth Amendment. The
Court has repeatedly stressed that individuals at the border have a lower expectation of privacy
and that the “[t]he Fourth Amendment balance between the interests of the Government and the
privacy right of the individual is [] struck much more favorably to the Government . . . .”410 The
Second Circuit has noted that collecting fingerprints, a type of biometric identifier, at a land port
of entry was a routine search, meaning that no reasonable suspicion was required.411 In addition,
the collection of other biometric information, such as facial geometry or walking gait, likely does
not raise constitutional concerns. The Supreme Court has observed that persons generally do not
have a Fourth Amendment interest in “physical characteristics ... constantly exposed to the
public,” such as the tone of their voice or facial features.412 In short, current jurisprudence
suggests that minimally intrusive collection of biometric data, such as the collection and
comparison of facial geometry, at the border likely does not implicate the Fourth Amendment.
Still, as discussed above, depending on the level of intrusion, some searches performed at the
international border may be classified as nonroutine and therefore require reasonable suspicion.413
In the event of a challenge to a method of biometric collection as nonroutine, a reviewing court
may find the Supreme Court’s 2013 decision Maryland v. King instructive.414 In that case, the
Court considered the constitutionality of the collection of an arrestee’s DNA as a part of routine
booking procedure in the U.S. interior.415 The Court observed that wiping a buccal swab on the
inside tissues of a person’s cheek to obtain DNA samples is a “search” subject to Fourth
Amendment scrutiny because any “intrusio[n] into the human body” invades personal security.416
The Court reasoned that the government’s interest—including the “need for law enforcement
officers in a safe and accurate way to process and identify the persons and possession they must

409 See, e.g., Stephanie Beasley, Big Brother on the U.S. Border?, POLITICO (Oct. 9, 2019),
https://www.politico.com/agenda/story/2019/10/09/us-border-biometrics-001250/.
410 United States v. Montoya de Hernandez, 473 U.S. 531, 539–40 n.4 (1985).
411 Tabbaa v. Chertoff, 509 F.3d 89, 99 (2d Cir. 2007). See also Davis v. Mississippi, 394 U.S. 721, 728 (1969). The
Supreme Court has held that the collection of one such identifier—fingerprints—did not raise Fourth Amendment
concerns when done in the interior of the United States. Id. The Court upheld police collection of lawfully arrested
persons’ fingerprints, describing this practice as minimally intrusive because it “involves none of the probing into an
individual’s private life and thoughts that marks an interrogation or search.” Id. at 727.
412 In United States v. Dionisio, 410 U.S. 1 (1973), the Supreme Court held that a grand jury directive for a witness to
give a voice exemplar did not constitute an infringement of the witness’s Fourth Amendment rights. In so doing, the
Court opined:
In Katz . . . we said that the Fourth Amendment provides no protection for what a person
knowingly exposes to the public, even in his own home or office. . . . The physical characteristics
of a person's voice, its tone and manner, as opposed to the content of a specific conversation, are
constantly exposed to the public. Like a man's facial characteristics, or handwriting, his voice is
repeatedly produced for others to hear. No person can have a reasonable expectation that others will
not know the sound of his voice, any more than he can reasonably expect that his face will be a
mystery to the world.
Id. at 14 (internal quotations marks omitted).
413 See Montoya de Hernandez, 473 U.S. at 537–38 (discussing Fourth amendment reasonableness requirement at the
border).
414 Maryland v. King, 569 U.S. 435 (2013).
415 Id.
416 Id. at 447 (quoting Schmerber v. California, 384 U.S. 757, 770 (1966)). This is contrast to the collection of other
nonobtrusive forms of personal identifiers, such as the capturing of facial geometry or walking gait.
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take into custody”—substantially outweighed the arrestee’s interest in limiting the intrusion of the
cheek swab.417 Although King involved a challenge to a “search” in the interior of the United
States, the Court’s opinion suggests that in a challenge to the collection of biometric information
by designated officers at the border, a reviewing court would likely (1) consider whether the
collection of the personal identifier was a “search” subject to Fourth Amendment scrutiny418; (2)
evaluate whether the Fourth Amendment requires that the officer have some level of
particularized suspicion419; and (3) weigh “the promotion of legitimate governmental interests”
against “the degree to which [the search] intrudes upon an individual’s privacy.”420
In any event, the border search exception and an officer’s broad authority to conduct searches at
the border suggest that constitutional challenges to the collection of biometric identifiers would
face significant obstacles, at least so long as the collection was done in a minimally intrusive
manner. Still, while the Constitution provides a baseline for government conduct, Congress may
consider legislation to promote or constrain the collection of biometric data.
Racial Profiling
As discussed in this report, immigration authorities may conduct roving patrols and set up
checkpoints near the border to deter the unlawful entry of aliens and contraband further into the
interior of the United States.421 In United States v. Brignoni-Ponce, the Supreme Court held that
Border Patrol officers could not solely consider a person’s ethnic appearance when making a
roving patrol stop, but suggested it can be considered with other “relevant factors” to establish
reasonable suspicion.422 In United States v. Martinez-Fuerte, where the Court held that
immigration checkpoint stops require no reasonable suspicion, the Court opined that a person
could be briefly detained at the checkpoint’s “secondary inspection” area “on the basis of criteria
that would not sustain a roving-patrol stop,” and continued that “even if it be assumed that such
referrals are made largely on the basis of apparent Mexican ancestry, we perceive no
constitutional violation.”423
There has been some debate as to whether the Supreme Court’s reliance on ethnic appearance as a
factor in border-related searches and seizures can still hold sway nearly 50 years later, given the
changing demographics of the southwestern United States and its increased Hispanic

417 Id. at 449.
418 Id. at 447 (establishing that wiping a buccal swab on the inside tissues of a person’s cheek to obtain DNA samples is
a search subject to Fourth Amendment scrutiny because any “intrusio[n] into the human body” invades personal
security).
419 See id. at 448. The Court noted that the collection of DNA was standard booking procedure of arrestees under
Maryland law, removing a need for a neutral magistrate to evaluate whether probable cause supports the search because
officers do not have discretion. Id. Because a probable cause determination was irrelevant, the Court explained, the
Fourth Amendment solely required an examination of the reasonableness—both in scope and manner of execution—of
this “search.” Id.
420 Id.
421 United States v. Arvizu, 534 U.S. 266, 277–78 (2002); United States v. Cortez, 449 U.S. 411, 417–18 (1981);
United States v. Martinez-Fuerte, 428 U.S. 543, 545 (1976); United States v. Ortiz, 422 U.S. 891, 896–97 (1975);
United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975); Almeida-Sanchez v. United States, 413 U.S. 266, 274–75
(1973).
422 Brignoni-Ponce, 422 U.S. at 886–87 (“The likelihood that any given person of Mexican ancestry is an alien is high
enough to make Mexican appearance a relevant factor, but standing alone it does not justify stopping all Mexican-
Americans to ask if they are aliens.”).
423 Martinez-Fuerte, 428 U.S. at 563.
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population.424 In more recent decades, some courts have limited, on Fourth Amendment grounds,
the government’s ability to consider race or ethnic appearance during roving patrol stops and
other border-related detentions. In United States v. Montero-Camargo, the Ninth Circuit
considered a challenge to a roving patrol stop of two individuals near the U.S.-Mexico border that
was based, in part, on their Hispanic appearance.425 The court held that the officers could not
consider the individuals’ ethnic appearance to establish reasonable suspicion, even if it was not
the only factor considered, because the stop occurred in an area with a large Hispanic
population.426 The court described the Supreme Court’s identification of ethnic appearance as a
“relevant factor” in Brignoni-Ponce as “brief dictum” based on “now-outdated demographic
information” about the Hispanic population in the United States, which had grown substantially
since the Court’s 1975 decision.427 Thus, the Ninth Circuit determined, ethnic appearance serves
“little or no use” in deciding whether someone should be stopped near the southern border.428
Nevertheless, the court concluded that the stop in question was permissible because other factors
relied upon by the officers independently established reasonable suspicion.429
In another case, a federal district court considered a constitutional challenge to the detention of
two airline passengers that was based, in part, on their Arab ethnicity.430 In response to a lawsuit
challenging the detention on Fourth Amendment grounds, the government argued that, under
Brignoni-Ponce, the passengers’ ethnicity was a “relevant factor” in establishing either reasonable
suspicion or probable cause that they were conducting “terrorist surveillance or probing
operations.”431 The court declared that ethnicity “has no probative value in a particularized
reasonable-suspicion or probable cause determination” because it has no bearing on a person’s
propensity to commit a crime.432 Like the Ninth Circuit, the court determined that Brignoni-
Ponce’s “dictum” regarding the consideration of ethnic appearance for immigration-related stops
was based on demographic data that did not reflect more recent changes in the U.S. population.433

424 See, e.g., Renata Ann Gowie, Driving While Mexican: Why the Supreme Court Must Reexamine United States v.
Brignoni-Ponce, 422 U.S. 873 (1975), 23 HOUS. J. INT’L L. 233, 252 (2001) (“What may have been true in 1975 is no
longer true today. The increased Hispanic presence in the southwestern United States and the proliferation of minivans,
sport utility vehicles, and other large vehicles make much of Brignoni-Ponce’s analysis untenable.”).
425 United States v. Montero-Camargo, 208 F.3d 1122, 1128–29 (9th Cir. 2000).
426 Id. at 1132, 1135.
427 Id. at 1132–33.
428 Id. at 1134; see also id. (“Reasonable suspicion requires particularized suspicion, and in an area in which a large
number of people share a specific characteristic, that characteristic casts too wide a net to play any part in a
particularized reasonable suspicion determination.”) (emphasis in original); United States v. Raygoza-Garcia, 902 F.3d
994, 1003 (9th Cir. 2018) (“[W]e have held that where a large portion of the area’s population is Latino, officers cannot
rely on an individual’s apparent Latino appearance in making a reasonable suspicion determination because one’s
ethnicity or race is not sufficiently particularized to indicate the criminality of a particular person.”) (citing United
States v. Manzo-Jurado, 457 F.3d 928, 935 n.6 (9th Cir. 2006)).
429 Montero-Camargo, 208 F.3d at 1137–39. The court observed that the individuals who were stopped made U-turns
on a highway, at a place where the Border Patrol officers’ view was obstructed; they stopped briefly in an area
frequently used for illegal activities, before going back in the direction from which they had come; and their vehicles
had Mexicali license plates. Id.
430 Farag v. United States, 587 F. Supp. 2d 436, 442 (E.D.N.Y. 2008).
431 Id. at 449, 460, 463.
432 Id. at 464.
433 Id. at 464–65; see also Melendres v. Arpaio, 989 F. Supp. 2d 822, 898–99 (D. Ariz. 2013) (holding that policy of
sheriff’s office to use race or Hispanic appearance as a factor in determining whether there was reasonable suspicion to
stop a vehicle, including for an immigration investigation, violated the Fourth Amendment).
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Some courts have allowed immigration officers to consider race or ethnic appearance in
conjunction with other factors in certain circumstances. In United States v. Manzo-Jurado, the
Ninth Circuit clarified that an individual’s apparent Hispanic appearance is not a relevant factor
for purposes of the Fourth Amendment “in regions heavily populated by Hispanics.”434 But the
court determined that Border Patrol officers could consider the Hispanic appearance of a work
crew in an area near the U.S.-Canada border that was “sparsely populated by Hispanics.”435 While
the court found that this characteristic might sometimes be a relevant factor for establishing
reasonable suspicion, it ultimately concluded that the cumulative factors relied upon by Border
Patrol in the present case were insufficient. Specifically, the collected factors identified by Border
Patrol, according to the court, included “no additional information distinguishing any group
member from an ordinary, lawful immigrant.”436
Outside the Ninth Circuit, other courts have allowed the use of race or ethnic appearance for
Border Patrol stops, regardless of whether they occurred near the northern or southern border. For
instance, the Tenth Circuit has stated that, although ethnic appearance alone fails to establish
reasonable suspicion, “the Court in Brignoni-Ponce explained that ‘Mexican appearance [is] a
relevant factor’ when the stop occurs near the United States-Mexico border.”437 Similarly, citing
Brignoni-Ponce, the Fifth Circuit has stated that “ethnic appearance may be considered as one of
the relevant factors in supporting a reasonable suspicion that a vehicle is involved in the
transportation of illegal aliens.”438
Although some courts have allowed Border Patrol officers to consider race or ethnicity when
making investigatory stops for purposes of the Fourth Amendment, DHS more recently
implemented a policy that prohibits consideration of race or ethnicity during law enforcement
activities “in all but the most exceptional instances.”439 According to the agency, immigration
officers may consider race or ethnicity only when there is a “compelling governmental interest”
present, and the officers exercise their authority “in a way narrowly tailored to meet that
compelling interest.”440 The agency’s policy does not preclude consideration of race or ethnicity
if that information is “specific to particular suspects or incidents” (e.g., to identify a suspect).441

434 United States v. Manzo-Jurado, 457 F.3d 928, 935 n.6 (9th Cir. 2006) (citing Montero-Camargo, 208 F.3d at 1132).
435 Id.
436 Id. at 940.
437 United States v. Lopez-Martinez, 25 F.3d 1481, 1487 (10th Cir. 1994) (quoting Brignoni-Ponce, 422 U.S. at 886–
87).
438 United States v. Hernandez-Moya, 353 F. App’x 930, 934 (5th Cir. 2009) (citing Brignoni-Ponce, 422 U.S. at 886–
87 (1975); see also United States v. Morales, 191 F.3d 602, 606–07 (5th Cir. 1999) (concluding that the fact that the
name on a vehicle registration was inconsistent with the Hispanic appearance of the owner of the vehicle could, in
combination with other factors, establish reasonable suspicion for a Border Patrol stop).
439 See Memorandum from Janet Napolitano, Sec’y of DHS to DHS Component Heads, The Department of Homeland
Security’s Commitment to Nondiscriminatory Law Enforcement and Screening Activities (Apr. 26, 2013),
https://www.cbp.gov/about/eeo-diversity/policies/nondiscrimination-law-enforcement-activities-and-all-other-
administered. Under the policy, racial profiling is defined as “the invidious use of race or ethnicity as a criterion in
conducting stops, searches, and other law enforcement, investigation, or screening activities.” Id. The policy notes that
racial profiling “is premised on the erroneous assumption that any particular individual of one race or ethnicity is more
likely to engage in misconduct than any particular individual of another race or ethnicity.” Id. See also U.S. Customs &
Border Prot., CBP Policy on Nondiscrimination in Law Enforcement Activities and All Other Administered Programs
(Feb. 24, 2020), https://www.cbp.gov/about/eeo-diversity/policies/nondiscrimination-law-enforcement-activities-and-
all-other-administered (describing nondiscrimination policy).
440 See Memorandum, supra note 439. According to CBP, national security “is per se a compelling interest.” See CBP
Policy on Nondiscrimination in Law Enforcement Activities and All Other Administered Programs, supra note 439.
441 See Memorandum, supra note 439.
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Despite these measures, some contend that immigration officers have continued to rely on race or
ethnicity when conducting immigration-related stops near the border.442 And courts have
continued to address Fourth Amendment challenges to immigration or other government
authorities’ consideration of race or ethnicity during border enforcement activities.443
While border stops based on race or ethnic appearance may raise Fourth Amendment concerns,
such stops may also violate the constitutional right to equal protection.444 The principle of equal
protection serves as “the constitutional basis for objecting to intentionally discriminatory
application of laws,”445 and provides protection against discriminatory law enforcement actions
even if there is sufficient level of suspicion to justify those actions under the Fourth
Amendment.446 Thus, an otherwise lawful border stop (e.g., a checkpoint detention) that is
motivated by a person’s race or ethnicity could constitute an equal protection violation.447 For that
reason, apart from Fourth Amendment challenges, courts have considered equal protection
challenges to border stops allegedly based on racial profiling.448

442 See, e.g., First Am. Compl. for Damages and Injunctive Relief and Request for Jury Trial, Suda v. U.S. Customs &
Border Prot., No. CV-19-10-GF-BMM (D. Mont. Jan. 29, 2020) (claiming that a CBP officer unlawfully detained two
U.S. citizens at a store in Havre, MT, solely because they were speaking Spanish); Compl., Owunna v. United States,
No. 1:18-cv-00536-LMB-MSN (E.D. Va. May 3, 2018) (alleging that a U.S. citizen returning from Nigeria was
unlawfully detained by CBP officials because of his perceived race or ethnicity).
443 See Millan-Hernandez v. Barr, 965 F.3d 140, 149 (2d Cir. 2020) (holding that alien presented sufficient evidence
that she was detained by police and CBP officers because of her race or ethnicity to warrant a hearing on whether
evidence of her alienage should have been suppressed in her removal proceedings); Sanchez v. Sessions, 904 F.3d 643,
650–51 (9th Cir. 2018) (holding that Coast Guard officers violated alien’s Fourth Amendment rights by detaining him
based solely on his race absent reasonable suspicion of unlawful activity); Muniz-Muniz v. U.S. Border Patrol, 869
F.3d 442, 447 (6th Cir. 2017) (rejecting claim that Border Patrol agents had a policy of targeting Hispanics in making
stops); Martin-Perez v. Barr, 783 F. App’x 772, 773–74 (9th Cir. 2019) (declining to suppress evidence of the identity
of an alien placed in formal removal proceedings despite claim that arrest by Border Patrol officers was based solely on
perceived Mexican ethnicity); Arriaga-Hernandez v. Att’y Gen., 712 F. App’x 151, 153 (3d Cir. 2017) (same).
444 See U.S. CONST. amend. XIV, § 1 (providing that no state may “deny to any person within its jurisdiction the equal
protection of the laws”). Although the Fourteenth Amendment applies to the states, the principles of equal protection
are applied to the federal government through the Fifth Amendment’s Due Process Clause. Bolling v. Sharpe, 347 U.S.
497, 499–500 (1954).
445 Whren v. United States, 517 U.S. 806, 813 (1996).
446 See Farm Labor Org. Comm. v. Ohio State Highway Patrol, 308 F.3d 523, 533 (6th Cir. 2002) (“Similarly, the
Supreme Court, in Whren v. United States, confirmed that an officer’s discriminatory motivations for pursuing a course
of action can give rise to an Equal Protection claim, even where there are sufficient objective indicia of suspicion to
justify the officer’s actions under the Fourth Amendment.”) (citing Whren, 517 U.S. at 813).
447 To establish an equal protection violation, a plaintiff must show that a law enforcement policy had a discriminatory
effect and that it was motivated by a discriminatory purpose. Wayte v. United States, 470 U.S. 598, 608 (1985). An
equal protection claim can also be established by showing a facially discriminatory enforcement policy. Id. at 608 n.10.
448 See, e.g., Muniz-Muniz, 869 F.3d at 444–47 (ruling that plaintiffs failed to show that the Border Patrol had any
policy or widespread practice allowing consideration of race during investigatory stops for purposes of establishing an
equal protection claim); Farm Labor Org. Comm. v. U.S. Border Patrol, 162 F. Supp. 3d 623, 638–41 (N.D. Ohio 2016)
(ruling that plaintiffs failed to show that Border Patrol engaged in a pattern of racially profiling Hispanics during
immigration enforcement operations); Melendres v. Arpaio, 989 F. Supp. 2d 822, 902–05 (D. Ariz. 2013) (concluding
that policy of sheriff’s office to use race as a factor in forming reasonable suspicion to detain aliens on the basis of
immigration status violated equal protection).
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Recent Legislation Concerning the Government’s
Border Search Authority
In recent years, legislation has been introduced in Congress that would clarify the government’s
ability to conduct searches and seizures at the border and surrounding regions. Generally, the
legislation would restrict DHS’s ability to conduct warrantless searches and seizures.
Some legislation would clarify CBP’s ability to conduct searches in areas that primarily fall under
the jurisdiction of another agency. For example, the Securing our Borders and Wilderness Act
introduced in the 117th Congress would authorize CBP to engage in certain activities, including
using aircraft, conducting patrols, and search and rescue operations, within federally owned areas
near the international border that are designated as “wilderness areas.”449
Some introduced bills would change the “border zone,” the area generally extending 100 miles
from the border where immigration officers may stop and search vehicles and vessels without a
warrant.450 For instance, the Border Zone Reasonableness Restoration Act introduced in the 116th
Congress would have amended INA Section 287(a)(3) by limiting officers’ ability to board and
search vehicles, trains, aircraft, vessels, and other conveyances to areas within 25 miles of the
border.451 Immigration officers also would have been barred from conducting highway
immigration checkpoints more than 10 miles from the border unless there is reasonable suspicion
that a person in the vehicle “is inadmissible or otherwise not entitled to enter or remain in the
United States.”452 The bill would have also generally prohibited officers from considering race,
ethnicity, gender, national origin, religion, or sex (including sexual orientation and gender
identity) during checkpoint operations.453 Finally, immigration officers would have had access to
private lands (but not dwellings) for patrolling the border only within 10 miles from the border
(under current law that authority extends to 25 miles from the border).454
Other recent bills would have restricted DHS’s ability to search electronic devices at the border.
Courts have held that CBP officers may conduct limited, manual searches of cell phones and
other electronic devices without a warrant, probable cause, or any suspicion of unlawful
activity.455 As discussed previously, courts have split on whether more advanced, forensic
searches require reasonable suspicion.456 A bill introduced in the 116th Congress would have
allowed a manual electronic device search only upon reasonable suspicion that (1) the individual

449 Securing Our Borders and Wilderness Act, H.R.760, 117th Cong. § 2 (2021).
450 8 U.S.C. § 1357(a)(3); 8 C.F.R. § 287.1(a)(2).
451 Border Zone Reasonableness Restoration Act of 2019, S.2180, 116th Cong. § 2(a)(5) (2019); Border Zone
Reasonableness Restoration Act of 2019, H.R.3852, 116th Cong. § 2(a)(5) (2019). The Secretary of Homeland Security
would have authority to expand the area in which immigration officers may board vehicles, vessels, aircraft, trains, and
other conveyances to more than 25 miles from the border (but no greater than 100 miles) for certain sectors or districts
in limited circumstances. Id.
452 Id. The Secretary of Homeland Security would have authority to expand the area in which immigration officers can
conduct suspicionless checkpoints to more than 10 miles from the border (but no greater than 25 miles) for certain
sectors or districts in some circumstances. Id.
453 Id.
454 Id.; see also 8 U.S.C. § 1357(a)(3).
455 See Alasaad v. Mayorkas, 988 F.3d 8, 19 (1st Cir. 2021); United States v. Arnold, 533 F.3d 1003, 1008–10 (9th Cir.
2008); United States v. Ickes, 393 F.3d 501, 506 (4th Cir. 2005).
456 See United States. v. Touset, 890 F.3d 1227, 1233 (11th Cir. 2018); United States v. Kolsuz, 890 F.3d 133, 145–46
(4th Cir. 2018); United States v. Cotterman, 709 F.3d 952, 960, 966 (9th Cir. 2013).
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transporting the device is carrying contraband or engaged in certain other specified activity, and
(2) the device contains evidence relevant to the contraband or specified activity.457 The bill would
have permitted a forensic search (which is broadly defined to include a search that uses software
or external equipment, involves copying of data, is conducted for more than four hours, or is
conducted manually with the entry of a password) only with a warrant.458
A separate bill in the 116th Congress, the Protecting Data at the Border Act, would have
prohibited CBP from accessing the digital contents of an electronic device belonging to a “United
States person” (defined to include a U.S. citizen and a lawful permanent resident) without a
warrant supported by probable cause; and denying a United States person’s entry into or exit from
the United States based on his or her refusal to provide access to the device.459 If a United States
person consents to providing access to an electronic device, the bill would have required the
government to obtain the consent in writing (with written advisals that access to the device cannot
be compelled without a valid warrant) before accessing the device.460 The bill also would have
provided for certain “emergency exceptions” to the warrant requirement (e.g., an emergency
situation involving potential death or serious physical injury to any person).461
Legislation focused primarily on drone surveillance was last introduced in the 115th Congress.
For example, the Drone Aircraft Privacy and Transparency Act would have prohibited a
government agency from using an unmanned aircraft system (or requesting information collected
by another person using an unmanned aircraft system) without a warrant, unless there are
“exigent circumstances.”462 The Preserving American Privacy Act would have similarly barred
government agencies from using unmanned aircraft systems for law enforcement purposes
without a warrant, but would create exceptions including emergency circumstances (e.g.,
imminent death of serious physical injury to a person) and Border Patrol operations within 25
miles of the border.463

457 A Bill to Place Restrictions on Searches and Seizures of Electronic Devices at the Border, S.2694, 116th Cong.
§ 2(b) (2019).
458 Id. §§ 1, 2(d). The bill would have allowed the seizure of an electronic device only upon probable cause that (1) the
individual is carrying contraband or engaged in certain other specified activity, or has violated any law punishable by
more than one-year imprisonment, and (2) the device contains evidence related to the contraband, specified unlawful
activity, or criminal violation. Id. § 2(c).
459 Protecting Data at the Border Act, S.1606, 116th Cong. § 4(a) (2019); Protecting Data at the Border Act, H.R.2925,
116th Cong. § 4(a) (2019). The bill would have also prohibited the government from delaying a United States person’s
entry into or exit from the United States for more than 4 hours pending a determination as to whether that person will
consent to providing access to the device. Id. § 4(a)(3).
460 Id. § 4(c).
461 Id. § 4(b).
462 Drone Aircraft Privacy and Transparency Act of 2017, S.631, 115th Cong. § 340 (2017); Drone Aircraft Privacy and
Transparency Act of 2017, H.R.1526, 115th Cong. § 340 (2017). “Exigent circumstances” would exist if “a law
enforcement entity reasonably believes there is an imminent danger of death or serious physical injury,” or “a law
enforcement entity reasonably believes there is a high risk of an imminent terrorist attack by a specific individual or
organization and the Secretary of Homeland Security has determined that credible intelligence indicates there is such a
risk.” Id.
463 Preserving American Privacy Act of 2018, H.R.6617, 115th Cong. § 3119c (2018).
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Appendix.
The following tables provide (1) an overview of federal statutes authorizing warrantless customs searches and boarding of vessels; (2) an
overview of federal statutes authorizing warrantless searches and seizures by immigration officers; and (3) a comparison of the requirements for
searches and seizures at the border and surrounding regions.
Table A-1. Federal Statutes Authorizing Warrantless Customs Searches and Boarding of Vessels
Federal Statute
Scope of Search or Seizure
Enforcing Agency
Location of Search or Seizure
14 U.S.C. § 522
Authorizes boarding of any vessel “subject to the jurisdiction, or to the
Coast Guard
Vessels on the high seas and waters
operation of any law, of the United States” to question occupants,
over which United States has
examine documentation, and conduct inspections and searches
jurisdiction
Also permits arrests for violations of federal law and seizure of vessel or
merchandise
19 U.S.C. § 482
Authorizes, pursuant to the boarding of a vessel under 19 U.S.C. § 1581,
CBP/Coast Guard
Vessels in the United States or within
the search of “any vehicle, beast, or person” on the vessel that is
customs waters (i.e., within 12 nautical
suspected of carrying merchandise subject to customs duties or that has
miles of the coast)
been brought into the United States unlawful y
Also authorizes the search of “any trunk or envelope” on the vessel for
which there is “reasonable cause” to suspect there is merchandise
unlawful y brought to the United States
19 U.S.C. § 1467
Authorizes the inspection of persons, baggage, and merchandise arriving
CBP/Coast Guard
At the border (e.g., a port of entry)
in the United States by vessel from a foreign port
19 U.S.C. § 1496
Allows the examination of baggage of any person arriving in the United
CBP/Coast Guard
At the border (e.g., a port of entry)
States
19 U.S.C. § 1581
Permits boarding of a vehicle or vessel to examine documentation and to
CBP/Coast Guard
Vehicles or vessels found in “any place
inspect and search the vehicle or vessel (including any person, trunk,
in the United States” or “within the
package, or cargo on board)
customs waters” (i.e., within 12 nautical
Also authorizes seizure of vehicle or vessel that is subject to forfeiture,
miles of the coastline)
fine, or penalty
19 U.S.C. § 1583
Authorizes search of international mail
CBP/Coast Guard
At the border
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Federal Statute
Scope of Search or Seizure
Enforcing Agency
Location of Search or Seizure
19 U.S.C. § 1589a
Permits warrantless arrests for any criminal offense under federal law
CBP/Coast Guard
Anywhere in the United States or
committed in the officer’s presence; or for any felony under federal law
within customs waters (i.e., within 12
committed outside the officer’s presence if there are reasonable grounds
nautical miles of the coast)
to believe the suspect has committed the felony
Source: 6 U.S.C. §§ 202, 211(c); 14 U.S.C. § 522(a); 19 U.S.C. §§ 482(a), 1401(j), 1467, 1496, 1581(a), 1581(e), 1583(a)(1), 1589a(3), 1709(b), 1709(c); 19 C.F.R. § 101.1.

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Table A-2. Federal Statutes Authorizing Warrantless Searches and Seizures by Immigration Officers
Statutory Provision
Scope of Search or Seizure
Location of Search or Seizure
8 U.S.C. § 1357(a)(1)
Interrogation of any person believed to be an alien
Anywhere within the United States or at the border
concerning his or her right to be or remain in the
United States
8 U.S.C. § 1357(a)(2)
Arrest of alien entering or attempting entry into the
Anywhere within the United States or at the border
United States unlawful y
Arrest of alien if there is “reason to believe” alien is in
United States unlawful y and likely to escape before a
warrant can be obtained
8 U.S.C. § 1357(a)(3)
Boarding of vessels, railway cars, aircraft, conveyances,
Within a “reasonable distance” of any “external
and vehicles to search for aliens.
boundary” of the United States. DHS regulations

generally define “reasonable distance” as within 100 air
miles from any external boundary or any shorter
Access to private lands (but not dwellings) for the
distance set by immigration authorities within a
purpose of patrol ing the border
particular sector or district; in “unusual
circumstances” a reasonable distance may be set that
is greater than 100 air miles from an external
boundary

Within 25 miles from any external boundary
8 U.S.C. § 1357(a)(4)
Arrests for felonies under any federal law regulating
Anywhere within the United States or at the border
the admission or removal of aliens (e.g., unlawful
reentry) if there is reason to believe the arrested
person is guilty of the felony and there is a likelihood
of the person escaping before an arrest warrant can be
secured
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Statutory Provision
Scope of Search or Seizure
Location of Search or Seizure
8 U.S.C. § 1357(a)(5)
Arrests for any felony under federal law committed in
Anywhere within the United States or at the border
the immigration officer’s presence, if the officer is
performing duties relating to the enforcement of
immigration laws and there is a likelihood of the
person escaping before a warrant can be secured
Arrests for any felony under federal law if the
immigration officer has reasonable grounds to believe
the arrested person has committed the felony, if the
officer is performing duties relating to enforcement of
immigration laws and there is likelihood of the person
escaping before a warrant can be secured
8 U.S.C. § 1357(c)
Search of a person (and his or her personal
Generally at the border
belongings) who is seeking admission to the United
States if there is “reasonable cause” to suspect there
are grounds for denying the person’s admission that
the search would disclose
Source: 8 U.S.C. §§ 1225(d)(1), 1357(a)(1), (a)(2), (a)(3), (a)(4), (a)(5), (c); 8 C.F.R. § 287.1(a)(1), (2).

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Table A-3. Judicial Requirements for Border-Related Searches and Seizures
General Scope of Search or
Type of Search or Seizure
Physical Location
Border Crossing Required
Seizure
Evidentiary Requirements
Border Searches
At the physical border itself or
Yes
Typically involves routine
No reasonable suspicion or
the functional equivalent of the
inspections and searches (e.g.,
probable cause required for
border (e.g., port of entry,
brief questioning and examining routine inspections and searches
border checkpoint,
luggage or merchandise)
Nonroutine inspections and
international airport)
searches (e.g., strip searches,
forensic cell phone searches)
may require at least reasonable
suspicion of criminal activity
Extended Border Searches
Generally occur in areas close
Yes
Covers the surveillance,
Requires (1) reasonable
to the border after a recent
pursuit, and search of an
certainty of a border crossing;
border crossing
individual who recently crossed (2) reasonable certainty that
the border and is suspected of
person or vehicle did not
committing a crime (e.g., drug
change condition since the
trafficking)
border crossing; and (3)
reasonable suspicion of a crime
Boarding of Vessels in Coastal
Inland waters with ready access No
Generally limited to a routine
No reasonable suspicion
or Interior Waterways
to the open sea, coastal
safety and document inspection required for routine boarding
waterways, or the high seas
in publicly accessible areas of
and inspection of vessel
the vessel
Limited searches of vessel may
require reasonable suspicion of
a crime
Exhaustive searches of vessel
(e.g., private living quarters)
require probable cause
Roving Patrols
Random patrols in certain areas No
Typically includes brief stop for
Reasonable suspicion required
away from the border (e.g.,
questioning about citizenship
for a vehicle stop
remote backroads), but not at
or immigration status, or any
Probable cause or consent is
fixed locations
“suspicious circumstances”
needed to search vehicle
May also include search of
(extended detention may also
vehicle and its occupants
require probable cause)

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General Scope of Search or
Type of Search or Seizure
Physical Location
Border Crossing Required
Seizure
Evidentiary Requirements
Immigration Checkpoints
Fixed locations away from the
No
A brief detention, routine
No reasonable suspicion
border (typically more than 25
questioning about citizenship
required for routine
miles from the border)
or immigration status, and
checkpoint stops
visual inspection of the vehicle
Extended detention may
Generally does not involve a
require at least reasonable
search of the vehicle or its
suspicion of a crime
occupants
Vehicle searches require

probable cause or consent
Transportation Checks
Bus or train stations near the
No
Boarding of bus or train to ask
Probably no reasonable
border
passengers about immigration
suspicion required for brief
status, travel plans, or luggage
stop and questioning
Extended detention likely
requires reasonable suspicion
or probable cause
Source: United States v. Drayton, 536 U.S. 194, 203–04 (2002); United States v. Arvizu, 534 U.S. 266, 273 (2002); Florida v. Bostick, 501 U.S. 429, 436 (1991); United
States v. Montoya de Hernandez, 473 U.S. 531, 538 (1985); United States v. Vil amonte-Marquez, 462 U.S. 579, 592–93 (1983); United States v. Cortez, 449 U.S. 411, 418
(1981); United States v. Ramsey, 431 U.S. 606, 619–20 (1977); United States v. Martinez-Fuerte, 428 U.S. 543, 566 (1976); United States v. Ortiz, 422 U.S. 891, 896–97
(1975); United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975); Almeida-Sanchez v. United States, 413 U.S. 266, 272–73 (1973); United States v. Stewart, 729 F.3d 517,
525 (6th Cir. 2013); United States v. Guzman-Padil a, 573 F.3d 865, 878–79 (9th Cir. 2009); United States v. Cardenas, 9 F.3d 1139, 1148 (5th Cir. 1993); United States v.
Roy, 869 F.2d 1427, 1430 (11th Cir. 1989); United States v. Herrera, 711 F.2d 1546 n.6 (11th Cir. 1983); United States v. Wil iams, 617 F.2d 1063, 1087 (5th Cir. 1980).
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Author Information

Hillel R. Smith
Kelsey Y. Santamaria
Legislative Attorney
Legislative Attorney

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