Updated February 17, 2021
The Law of Immigration Detention: A Brief Introduction
The Immigration and Nationality Act (INA) authorizes—
own recognizance (subject to certain conditions). In the
and in some cases requires—the Department of Homeland
event of an alien’s release, DHS may opt to enroll the alien
Security (DHS) to detain non-U.S. nationals (aliens) who
in an Alternatives to Detention program, which enables the
are subject to removal from the United States. This
agency to monitor and supervise the alien to ensure his or
detention scheme is multifaceted, with rules that turn on
her eventual appearance at a removal proceeding.
several factors, such as whether the alien is seeking
admission or has been lawfully admitted into the country;
INA § 236(a) permits an immigration officer, at any time
whether the alien has engaged in certain proscribed
during removal proceedings, to determine whether an
conduct; and whether the alien has been issued a final order
arrested alien should remain in custody or be released. If
of removal. This In Focus provides a brief introduction to
the alien is arrested without an administrative warrant, the
the immigration detention framework. For a more detailed
custody decision generally must be made within 48 hours.
discussion, see CRS Report R45915, Immigration
DHS regulations provide that to be released the alien must
Detention: A Legal Overview, by Hillel R. Smith.
show that he or she is not a flight or security risk.
Statutory Framework
If the alien remains detained, he or she may request review
Four provisions of the INA primarily shape the immigration
of DHS’s custody decision at a bond hearing before an
detention framework:
immigration judge (IJ) within the Department of Justice’s
Executive Office for Immigration Review (EOIR). The IJ
1. INA § 236(a) generally authorizes the detention
may decide whether DHS may retain physical custody or
of aliens pending a decision on whether the
release the alien, and the IJ has authority to set the bond
alien is to be removed from the United States
amount. The IJ’s custody determination may be appealed to
and permits those who are not subject to
the EOIR’s Board of Immigration Appeals (BIA). Federal
mandatory detention to be released on bond or
statute generally bars judicial review of a decision whether
their own recognizance;
to detain or release an alien, but courts may consider habeas
2. INA § 236(c) generally requires the detention of
corpus claims alleging that an alien’s detention is unlawful.
aliens who are removable because of specified
criminal activity or terrorism-related grounds;
Mandatory Detention of Criminal Aliens
While immigration officials generally have broad discretion
3. INA § 235(b) generally requires the detention
to decide whether to detain aliens during the pendency of
of applicants for admission who appear subject
removal proceedings, INA § 236(c) requires the detention
to removal, including aliens arriving at a port of
of aliens removable on specified criminal or terrorism-
entry and certain other aliens who have not been
related grounds. These grounds include, for example,
admitted or paroled into the United States; and
crimes involving moral turpitude, drug crimes, aggravated
4. INA § 241(a) generally requires an alien subject
felonies, and membership in a terrorist organization.
to a final order of removal to be held during the
90-day period when the alien’s removal is
INA § 236(c) states that DHS “shall take into custody any
effectuated, and DHS may detain an alien
alien” who falls within one of the enumerated criminal or
beyond this 90-day period if the agency is
terrorism-related grounds “when the alien is released” from
unable to effectuate removal and the alien falls
criminal custody. The Supreme Court in Nielsen v. Preap
within certain categories.
held that this mandatory detention scheme covers any alien
who has committed a specified offense, even if not
Discretionary Detention
immediately taken into custody after release from criminal
INA § 236(a) authorizes the arrest and detention of an alien
incarceration.
pending a determination on whether the alien shall be
removed from the United States. Detention under this
Except in limited circumstances, an alien detained under
statute is discretionary, and immigration authorities need
INA § 236(c) generally may not be released on bond or his
not continue to detain an alien subject to removal unless the
or her own recognizance during removal proceedings. The
alien is subject to mandatory detention (e.g., aliens
alien may seek limited review by an IJ to determine
convicted of specified crimes under INA § 236(c)).
whether he or she falls within one of the categories of aliens
subject to mandatory detention.
If DHS arrests and detains an alien under INA §236(a), and
the alien is not subject to mandatory detention, the agency
Mandatory Detention of Applicants for Admission
may either (1) continue to detain the alien during the
Under INA § 235(b) applicants for admission must
pendency of removal proceedings, or (2) release the alien
generally be detained for removal purposes if they do not
on bond in the amount of at least $1,500 or on the alien’s
https://crsreports.congress.gov

---

The Law of Immigration Detention: A Brief Introduction
appear clearly to be admissible. The statute defines an
in the reasonably foreseeable future. Following Zadvydas,
“applicant for admission” to include both an alien seeking
DHS established “special review procedures” to assess the
initial entry at a designated port of entry and an alien
likelihood of removal for aliens who remain detained
present in the United States who has not been admitted.
beyond the 90-day removal period. And in 2005, the
Supreme Court in Clark v. Martinez determined, as a matter
The detention requirements of INA § 235(b) have been
of statutory construction, that the presumptive six-month
construed to apply to applicants for admission regardless of
time limitation read into INA § 241(a) equally applied to
whether they are subject to a streamlined “expedited
aliens who had not been lawfully admitted into the United
removal” process (e.g., those apprehended when attempting
States, and who were being indefinitely detained after their
to enter the United States without valid entry documents) or
90-day periods.
are subject to formal removal proceedings (e.g., aliens
inadmissible because of engaging in certain criminal
Whether an alien’s prolonged detention during the
activities). This also includes aliens who, though initially
pendency of removal proceedings raises similar
subject to expedited removal, were found to have a credible
constitutional concerns remains debated. In 2003, the
fear of persecution if returned to their country of origin, and
Supreme Court in Demore v. Kim ruled that the mandatory
who were transferred to formal removal proceedings to
detention of certain aliens without bond (e.g., criminal
pursue asylum or similar forms of relief.
aliens) during removal proceedings is “constitutionally
permissible,” but the Court did not decide whether there are
DHS may “parole” an alien otherwise subject to detention
any constitutional limits to the duration of this detention.
under INA § 235(b) “for urgent humanitarian reasons or
Some lower courts, however, have construed Demore to
significant public benefit,” enabling the alien to be released
apply only to brief periods of detention, after which an alien
from the agency’s physical custody. Unlike custody
should have an opportunity to seek release on bond.
determinations under INA § 236(a), DHS’s parole decisions
are not subject to administrative review.
More recently, in Jennings v. Rodriguez, the Supreme Court
held that DHS has the statutory authority to detain aliens
Detention of Aliens After Removal Proceedings
potentially indefinitely during the pendency of removal
INA § 241(a) governs the detention of aliens subject to a
proceedings, but did not decide whether such prolonged
final order of removal. DHS “shall detain” an alien subject
detention is unconstitutional. But some lower courts have
to a final order of removal during a 90-day “removal
concluded that the detention of aliens during removal
period.” INA § 241(a) instructs that “under no circumstance
proceedings without a bond hearing violates due process if
during the removal period” may DHS release an alien
the detention is unreasonably prolonged, and that the
removable on certain criminal or terrorism-related grounds.
government bears the burden of proving at a bond hearing
The alien must be released on an order of supervision if not
that any continued detention is justified.
removed within the 90-day period.
In addition, a 1997 court settlement agreement known as
INA § 241(a) also provides that DHS may detain an alien
the Flores Settlement currently limits the period in which
ordered removed beyond this 90-day removal period if the
an alien minor may be detained by DHS. And under federal
agency is unable to effectuate removal and the alien falls
statute, an unaccompanied alien child who is subject to
within certain categories (e.g., criminal aliens, inadmissible
removal generally must be placed in the custody of the
aliens). DHS regulations provide that if the agency decides
Department of Health and Human Services, rather than
to keep the alien detained, it must conduct periodic custody
DHS, during the pendency of removal proceedings.
reviews to determine whether further detention is warranted
pending efforts to secure the alien’s removal to another
Apart from judicial constraints on the length of detention,
country. As discussed below, courts have recognized some
DHS’s detention authority may be restricted in other ways.
constitutional constraints to this detention.
For example, the agency has established certain standards
for the conditions of detention facilities, and detained aliens
Constitutional and Other Limitations to
have raised due process challenges to the conditions of their
DHS’s Detention Authority
confinement in some cases. And some courts have held that
DHS has broad statutory authority to detain aliens identified
the Fourth Amendment limits when immigration
for removal, but the scope of that authority may be subject
“detainers” may be used by DHS to take custody of aliens
to constitutional constraints, particularly if detention
from state and local law enforcement authorities.
becomes prolonged.
Thus, although DHS generally has broad detention
In 2001, the Supreme Court in Zadvydas v. Davis
authority, that authority is not unfettered, and due process
concluded that the indefinite detention of a lawfully
and other constitutional considerations may inform the
admitted alien ordered removed would raise “serious
duration and conditions of the alien’s detention.
constitutional concerns.” The Court construed INA § 241(a)
as having an implicit, temporal limitation of six months
Hillel R. Smith, Legislative Attorney
post-order of removal, after which an alien typically must
be released if there is no significant likelihood of removal
IF11343


https://crsreports.congress.gov

---

The Law of Immigration Detention: A Brief Introduction


Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
United States Government, are not subject to copyright protection in the United States. Any CRS Report may be
reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include
copyrighted images or material from a third party, you may need to obtain the permission of the copyright holder if you
wish to copy or otherwise use copyrighted material.

https://crsreports.congress.gov | IF11343 · VERSION 2 · UPDATED

---