Order Code RS20590
Updated May 19, 2003
CRS Report for Congress
Received through the CRS Web
The Posse Comitatus Act and Related
Matters: A Sketch
Jennifer Elsea
Legislative Attorney
American Law Division
Summary
The Posse Comitatus Act states that: Whoever, except in cases and under
circumstances expressly authorized by the Constitution or Act of Congress, willfully
uses any part of the Army or the Air Force as a posse comitatus or otherwise to execute
the laws shall be fined under this title or imprisoned not more than two years, or both.
18 U.S.C. § 1385. It reflects an American tradition that bridles at military involvement
in civilian affairs. Congress, however, has approved a number of instances where
extraordinary circumstances warrant a departure from the general rule, particularly in
cases where the armed forces provide civilian assistance without becoming directly
involved in civilian law enforcement. This is an abridged version of The Posse
Comitatus Act & Related Matters: The Use of the Military to Execute Civilian Law,
CRS Report 95-964 S in which the authorities for the statements made here may be
found. This report also summarizes proposed legislation that could result in increased
interaction between military and civil authorities.
Background
The Posse Comitatus Act, 18 U.S.C. § 1385, is perhaps the most tangible expression
of an American tradition , born in England and developed in the early years of our nation,
that rebels against military involvement in civilian affairs. The Declaration of
Independence listed among our grievances against Great Britain that the King had “kept
among us, in times of peace, Standing Armies without the consent of our legislatures,”
had “affected to render the Military independent of and superior to the civil power,” The
Articles of Confederation addressed the threat of military intrusion into civilian affairs by
demanding that the armed forces assembled during peacetime be no more numerous than
absolutely necessary for the common defense, and by entrusting control to civil authorities
within the states. The Constitution continued the theme. It provided that a civilian, the
President, should be the Commander in Chief of the Army and Navy of the United States
and that civilian authorities, the Congress, should be solely empowered to raise and
support Armies, provide and maintain a Navy, and make rules for their government and
regulation. The Bill of Rights limited the quartering of troops in private homes, U.S.
Congressional Research Service ˜ The Library of Congress

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Const. Amend. III, and noted that “a well regulated Militia, being necessary to the security
of a free State, the right of the people to keep and bear Arms, shall not be infringed,” U.S.
Const. Amend. II. The Constitution, on the other hand, explicitly permitted the Congress
to provide for calling out the militia to execute the laws, suppress insurrection, and repel
invasion, U.S. Const. Art. I, § 8, cl.16. Soon after Congress was first assembled under the
Constitution, it authorized the President to call out the militia, initially to protect the
frontier against “hostile incursions of the Indians,” and subsequently in cases of invasion,
insurrection, or obstruction of the laws. The President’s authority to call upon the state
militia to aid in putting down insurrections is reminiscent of the authority enjoyed by the
sheriff at common law to call upon the posse comitatus. In the beginning the two were
comparable but unrelated. Even though Congress empowered the President to call out the
militia to overcome obstructions to law enforcement, it continued to vest the federal
equivalent of the sheriff, the federal marshal, with the power to call forth the posse
comitatus in performance of his duties.
In some cases when it passed a particular statute Congress specifically authorized
recourse to the posse comitatus for its enforcement. Under the Fugitive Slave Act, for
instance, owners whose slaves had escaped to another state were entitled to an arrest
warrant for the slaves and to have the warrant executed by federal marshals. The marshals
in turn might “summon and call to their aid the bystanders, or posse comitatus of the
proper county . . . [and] all good citizens [were] commanded to aid and assist in the
prompt and efficient execution of this law, whenever their services may be required, as
aforesaid, for that purpose,” 9 Stat. 462, 463 (1850). Attorney General Caleb Cushing
declared that the “bystanders” contemplated by the Fugitive Slave Act might include
members of a state militia even when not in federal service, and in fact encompassed
members of the armed forces by virtue of their duties as citizens were part of the posse
comitatus.
Following the Civil War, the use of federal troops to execute the laws, particularly
in the states that had been part of the Confederacy, continued even after all other political
restrictions had been lifted. The Posse Comitatus Act was passed as part of an Army
appropriations bill in response. With exception of a reference to the Air Force, it has
remained essentially unchanged ever since, although Congress has authorized a
substantial number of exceptions and has buttressed the Act with an additional
proscription against use of the armed forces to make arrests or conduct searches and
seizures. While the war against terrorism has led some to call for a reexamination of the
role of the military in domestic law enforcement, Congress, in establishing the
Department of Homeland Security, expressed its sense reaffirming the continued
importance and applicability of the Posse Comitatus Act. 6 U.S.C. § 466.
When the Act Does Not Apply
Constitutional Exceptions: The Posse Comitatus Act does not apply “in cases and
under circumstances expressly authorized by the Constitution,” 18 U.S.C. § 1385. It has
been observed that the Constitution contains no provision expressly authorizing the use
of the military to execute the law, that the exception was included as part of a face-saving
compromise, and that consequently it should be ignored. The older commentaries suggest
that the word “expressly” must be ignored, for otherwise in their view the Posse
Comitatus Act is a constitutionally impermissible effort to limit the powers of the
President. The regulations covering the use of the armed forces during civil disturbances

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do not go quite that far, but they do assert two constitutionally based exceptions – sudden
emergencies and protection of federal property. The question of whether the constitutional
exception includes instances where the President is acting under implied or inherent
constitutional powers is one the courts have yet to answer.
Statutory Exceptions – Generally. The Posse Comitatus Act does not apply
where Congress has expressly authorized use of the military to execute the law. Congress
has done so in three ways, by giving a branch of the armed forces civilian law
enforcement authority, by establishing general rules for certain types of assistance, and
by addressing individual cases and circumstances with more narrowly crafted legislation.
Thus it has vested the Coast Guard, a branch of the armed forces, with broad law
enforcement responsibilities. Second, over the years it has passed a fairly extensive array
of particularized statutes, like those permitting the President to call out the armed forces
in times of insurrection and domestic violence, 10 U.S.C. §§ 331-335. Finally, it has
enacted general legislation authorizing the armed forces to share information and
equipment with civilian law enforcement agencies, 10 U.S.C. §§ 371-382.

These last general statutes were crafted to resolve questions raised by the so-called
Wounded Knee cases (see below). The legislation contains both explicit grants of
authority and restrictions on the use of that authority for military assistance to the police
– federal, state and local – particularly in the form of information and equipment, 10
U.S.C. §§ 371-382. Section 371 specifically authorizes the armed forces to share
information acquired during military operations and in fact encourages the armed forces
to plan their activities with an eye to the production of incidental civilian benefits. The
section allows the use of military undercover agents and the collection of intelligence
concerning civilian activities only where there is a nexus to an underlying military
purpose. Under sections 372 through 374, military equipment and facilities may be made
available to civilian authorities; members of the armed forces may train civilian police
on the operation and maintenance of equipment and may provide them with expert advice;
and military personnel may be employed to maintain and operate the equipment supplied.
The authority granted in sections 371-382 is subject to three general caveats. It may
not be used in any way that could undermine the military capability of the United States;
the civilian beneficiaries of military aid must pay for the assistance; and the Secretary of
Defense must issue regulations to ensure that the authority of sections 371 to 382 does not
result in use of the armed forces to make arrests or conduct searches and seizures solely
for the benefit of civilian law enforcement.
Military Purpose. The armed forces, when in performance of their military
responsibilities, are beyond the reach of the Posse Comitatus Act and its statutory and
regulatory supplements. Neither the Act nor its legislative history resolves the question
of whether the Act prohibits the Army from performing its military duties in a manner
which affords incidental benefits to civilian law enforcement officers. The courts and
commentators believe that it does not. As long as the primary purpose of an activity is
to address a military purpose, the activity need not be abandoned simply because it also
assists civilian law enforcement efforts.
Willfully Execute the Laws. The Act is limited to “willful” misuse of the Army
or Air Force. The Senate version of the original Act would have limited proscription to
“willful and knowing” violations, 7 Cong. Rec. 4302 (1878); the House version had no

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limitation, 7 Cong. Rec. 4181 (1878). The compromise which emerged from conference
opted to forbid only willful violations, but neither the statements of the managers nor
statements elsewhere in the debate explain what the limitation means. It seems unlikely
that a court would convict for anything less than a deliberate disregard of the law’s
requirements.
When has the Army or Air Force been used “to execute the laws”? Existing case law
and commentary indicate that “execution of the law” in violation of the Posse Comitatus
Act occurs (a) when the armed forces perform tasks ordinarily assigned not to them but
to an organ of civil government, or (b) when the armed forces perform tasks assigned to
them solely for purposes of civilian government. While inquiries may surface in other
contexts, such as the use of the armed forces to fight forest fires or to provide assistance
in the case of other natural disasters, Posse Comitatus Act questions arise most often
when the armed forces assist civilian police.
The tests used by most contemporary courts to determine whether military forces
have been used improperly as police forces in violation of the Posse Comitatus Act were
developed out of disturbances in 1973 at Wounded Knee on the Pine Ridge Indian
Reservation in South Dakota and inquire: (1) whether civilian law enforcement officials
made a direct active use of military investigators to execute the law; (2) whether the use
of the military pervaded the activities of the civilian officials; or (3) whether the military
was used so as to subject citizens to the exercise of military power which was regulatory,
prescriptive, or compulsory in nature.
Military Coverage
Navy & Marines. The Posse Comitatus Act proscribes use of the Army or the Air
Force to execute the law. It says nothing about the Navy, the Marine Corps, the Coast
Guard, or the National Guard. The courts have generally held that the Posse Comitatus
Act by itself does not apply to the Navy or the Marine Corps. They maintain, however,
that those forces are covered by similarly confining administrative and legislative
supplements, the most currently applicable of which appear in the DoD Directive.
Coast Guard. The Posse Comitatus Act likewise says nothing about the Coast
Guard. The Coast Guard is a branch of the armed forces, soon to be located within the
Department of Homeland Security, 14 U.S.C. § 1 (as amended), but relocated within the
Navy in time of war or upon the order of the President, 14 U.S.C. § 3. The Act will apply
to the Coast Guard while it remains part of the Department of Homeland Security. While
part of the Navy, it is subject to the orders of the Secretary of the Navy, 14 U.S.C. § 3, and
consequently to any generally applicable directives or instructions issued under the
Department of Defense or the Navy. As a practical matter, however, the Coast Guard is
statutorily authorized to perform law enforcement functions, 14 U.S.C. § 2. Even while
part of the Navy its law enforcement activities would come within the statutory exception
to the posse comitatus restrictions, and the restrictions applicable to components of the
Department of Defense would only apply to activities beyond those authorized.
National Guard. The Act is silent as to what constitutes “part” of the Army or Air
Force for purposes of proscription. There is little commentary or case law to resolve
questions concerning the coverage of the National Guard, the Civil Air Patrol, civilian
employees of the armed forces, or regular members of the armed forces while off duty.

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Strictly speaking, the Posse Comitatus Act predates the National Guard only in name
for the Guard “is the modern Militia reserved to the States by Art. I, § 8, cls.15, 16, of the
Constitution” which has become “an organized force, capable of being assimilated with
ease into the regular military establishment of the United States,” Maryland v. United
States, 381 U.S. 41, 46 (1965). There seems every reason to consider the National Guard
part of the Army or Air Force, for purposes of the Posse Comitatus Act, when in federal
service. When not in federal service, historical reflection might suggest that it is likewise
covered. Recall that it was the state militia, called to the aid of the marshal enforcing the
Fugitive Slave Act, which triggered Attorney General Cushing’s famous opinion. The
Posse Comitatus Act’s reference to “posse comitatus or otherwise” is meant to abrogate
the assertion derived from Cushing’s opinion that troops could be used to execute the law
as long as they were acting as citizens and not soldiers when they did so.
On the other hand, the National Guard is creature of both state and federal law, a
condition which as the militia it has enjoyed since the days of the Articles of
Confederation. Courts have held that members of the National Guard when not in federal
service are not covered by the Posse Comitatus Act. Similarly, the DoD directive is only
applicable to members of the National Guard when they are in federal service.
Off Duty, Acting as Citizens & Civilian Employees. The historical
perspective fares little better on the question of whether the Posse Comitatus Act extends
to soldiers who assist civilian law enforcement officials in a manner which any other
citizen would be permitted to provide assistance, particularly if they do so while off duty.
Congress passed the Act in response to cases where members of the military had
been used based on their civic obligations to respond to the call as the posse comitatus.
The debate in the Senate, however, suggests that the Act was not intended to strip service
members of all civilian rights and obligations. The more recent decisions, with the
endorsement of the commentators, have focused on the nature of the assistance provided
and whether the assistance is incidental to action taken primarily for a military purpose.

Some have questioned whether civilian employees of the armed forces should come
within the proscription of the Act, but most, frequently without comment, seem to
consider them “part” of the armed forces for purposes of the Posse Comitatus Act. The
current Defense Department Directive expressly includes civilian employees “under the
direct command and control of a military officer” within its Posse Comitatus Act policy
restrictions.
Geographical Application
It seems unlikely that the Posse Comitatus Act, by itself, applies beyond the confines
of the United States, its territories and possessions. It contains no expression of
extraterritorial application. Congress enacted it in response to problems occurring within
the United States and its territories, problems associated with the American political
process and policies and actions that promoted military usurpation of civilian law
enforcement responsibilities over Americans. It seems unlikely that its extraterritorial
application was either anticipated or intended. Congress does appear to have intended
the authority and restrictions contained in 10 U.S.C. §§ 371-382, however, to apply both
in the United States and beyond its borders.

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Consequences of Violation
Prosecution. The Posse Comitatus Act is a criminal statute under which there has
apparently never been a prosecution. It has been invoked with varying degrees of success,
however, to challenge the jurisdiction of the courts, as a defense in criminal prosecutions
for other offenses, as a ground for the suppression of evidence, as the grounds for, or a
defense against, civil liability, and as a means to enjoin proposed actions by the military.
Exclusion of Evidence. Allegations that the Posse Comitatus Act has been
violated are made most often by defendants seeking to exclude related testimony or
physical evidence, but most cases note the absence of an exclusionary rule, often avoiding
unnecessary analysis of the scope of the Act and whether a violation has occurred.
Jurisdiction & Criminal Defenses. Defendants have found the Act helpful in
prosecutions where the government must establish the lawfulness of its conduct as one
of the elements of the offense. Several defendants at Wounded Knee persuaded the court
that evidence of possible violations precluded their convictions for obstructing law
enforcement officials “lawfully engaged” in the performance of their duties.
Civil Liability. The Eighth Circuit has declared that a violation of the Act might
constitute an unreasonable search and seizure for purposes of the Fourth Amendment,
giving rise to a Bivens cause of action against offending federal officers or employees.
Compliance. The most significant impact of the Posse Comitatus Act is
attributable to compliance by the armed forces. As administrative adoption of the Act for
the Navy and Marines demonstrates, the military has a long standing practice of avoiding
involvement in civilian affairs which it believes are contrary to the Act, and which date
back to military acceptance of civilian authority since the founding of the Republic.
Proposed New Exceptions
H.R. 277 would amend title 10 to allow the Secretary of Defense to provide military
personnel to assist the Department of Homeland Security when necessary to respond to
“a threat to national security posed by the entry into the United States of terrorists, drug
traffickers, or illegal aliens.” Specially trained service members could be assigned to
assist the Bureau of Border Security and the U.S. Customs Service, but would not be
authorized to carry out searches, seizures, or other similar law enforcement activities. The
Department of Defense has been asked to provide comment on the bill.
S. 215 involves the National Guard while in service of the states and thus does not
implicate the Posse Comitatus Act. The bill, modeled after existing legislation that allows
the National Guard to play a role in the counterdrug program, would authorize the
Defense Department to provide funds to states to support approved plans for homeland
security activities that utilize the National Guard. The funds would be limited to paying
for expenses related to wages and other allowances for the National Guard personnel
performing homeland security duties while not in federal service.

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