Order Code RS21012
Updated February 6, 2004
CRS Report for Congress
Received through the CRS Web
Terrorism: Some Legal Restrictions on
Military Assistance to Domestic Authorities
Following a Terrorist Attack
Charles Doyle
Senior Specialist
American Law Division
Jennifer Elsea
Legislative Attorney
American Law Division
Summary
The Constitution empowers to the President to act as Commander in Chief of the
armed forces and to see to the execution of federal law; it gives Congress the authority
to make federal law including laws for the regulation of the armed forces. The Posse
Comitatus Act prohibits use of the armed forces to perform civilian governmental tasks
unless explicitly authorized to do so. There are statutory exceptions to ensure continued
enforcement of state and federal law, to provide disaster assistance, and to provide
technical support for law enforcement. There are constitutional impediments to the use
of the military to nationalize an industry, to try civilians, and to compel state officials
to perform federally-imposed duties. Unlawful use of the armed forces might result in
criminal or civil liability for responsible authorities and frustrate prosecution of
terrorists. For a more complete discussion, see CRS Report 95-964, The Posse
Comitatus Act & Related Matters: The Use of the Military to Execute Civilian Law.
The President is Commander in Chief of the armed forces of the United States and
is constitutionally charged to take care that the laws of the United States are faithfully
executed, U.S. Const. Art. II, §§2, 3. Congress is the repository of federal legislative
authority and is charged with the responsibility to make rules and regulations for the
governance of the armed forces of the United States, U.S. Const. Art. I, § 8, cl.14.
Authority not constitutionally vested in the national government, here or elsewhere, is
reserved to the states and the people, U.S. Const. Amends. X, IX.
Congress, through the Posse Comitatus Act (PCA), has forbidden use of the armed
forces to perform the tasks of civilian government in this country except where expressly
permitted by statute or the Constitution, 18 U.S.C. § 1385. The terrorist attacks of
September 11, 2001, prompted some calls for the increased use of the military to fight
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terrorism. While the USA PATRIOT Act (Pub. L. 107-56) broadened the permissible
circumstances for the use of the military to assist law enforcement agencies in countering
terrorism, Congress also reaffirmed its determination to maintain the principle of the
posse comitatus law, 6 U.S.C. § 466.
Statutory Exceptions to the PCA
Congress has provided the President with the authority to use military force to
enforce the law under a number of different circumstances. The President has explicit
statutory authority to use military personnel to suppress insurrection or to overcome
obstructions to or interference with the enforcement of federal or state law, 10 U.S.C. §§
331 to 333; and to grant the request of a state governor to use military resources to
perform emergency work for 10 days following a major disaster (with 75% of the cost to
be borne by the federal government), 42 U.S.C. § 5170b.
Chapter 18 of title 10, U.S. code (10 U.S.C. §§ 371-382) provides the authority for
and regulates the use of the military to support law enforcement agencies. The Secretary
of Defense has explicit statutory authority to permit assistance to federal, state and local
law enforcement (on a reimbursable basis, 10 U.S.C. § 377, without adversely affecting
military preparedness, 10 U.S.C. § 376, and without using personnel to conduct searches
or arrests, 10 U.S.C. § 375) in the form of sharing intelligence gathered in military
operations, 10 U.S.C. § 371; supplying military equipment and facilities, 10 U.S.C. § 372;
providing training and advice on the use and maintenance of equipment, 10 U.S.C. § 373;
and maintaining and operating equipment, 10 U.S.C. § 374. Department of Defense
personnel may be made available to federal law enforcement agencies to operate
equipment in conjunction with counter-terrorism operations (including the rendition of
a suspected terrorist from a foreign country) or the enforcement of counter-drug laws,
immigration laws, and customs requirements. Department of Defense personnel may
operate equipment for the purposes of detecting and monitoring air, ground, and sea
traffic; conducting aerial reconnaissance; intercepting vessels or aircraft near U.S.
borders; operating law enforcement base facilities overseas; transporting personnel and
facilitating communications in conjunction with the above activities; and transporting
suspected terrorists to the United States for trial, so long as the requesting law
enforcement agency maintains custody over the accused at all times,10 U.S.C. §
374(b)(2).
If the Attorney General and the Secretary of Defense jointly determine that an
emergency exists involving chemical or biological weapons of mass destruction, the
Secretary of Defense may provide resources and personnel to assist civil authorities, 10
U.S.C. § 382, subject to reimbursement, where such assistance is necessary for the
enforcement of sections 175 (prohibiting biological weapons) or § 2232c (repealed,
should probably refer to § 2232a – prohibiting the use of certain weapons of mass
destruction) of title 18, U.S. Code. However, military personnel may not make arrests,
participate directly in searches or seizures of evidence, or participate directly in
intelligence collection for law enforcement purposes, unless such action is necessary for
the immediate protection of human life and cannot be accomplished by law enforcement
personnel, 10 U.S.C. § 382(d)(2). Forms of assistance authorized under section 382
include the operation of equipment to monitor contain, disable, or dispose of the weapon
involved.

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The corresponding authority for the Attorney General to request military assistance
is found in 18 U.S.C. § 2332e. Unlike 10 U.S.C. § 382, however, the provision is not
limited to emergencies involving chemical and biological weapons, but was amended in
the PATRIOT Act (Pub. L. 107-56, § 104) to cover all weapons of mass destruction,
which are defined in 18 U.S.C. § 2332a to include:
(A) any destructive device as defined in section 921 of [] title 18[see below];
(B) any weapon that is designed or intended to cause death or serious bodily injury
through the release, dissemination, or impact of toxic or poisonous chemicals, or their
precursors;
(C) any weapon involving a disease organism; or
(D) any weapon that is designed to release radiation or radioactivity at a level
dangerous to human life.
A destructive device is defined under 18 U.S.C. § 921(a)(4) as:
(A) any explosive, incendiary, or poison gas-- (i) bomb, (ii) grenade, (iii) rocket
having a propellant charge of more than four ounces, (iv) missile having an explosive
or incendiary charge of more than one-quarter ounce, (v) mine, or (vi) device similar
to any of the devices described in the preceding clauses;
(B) any type of weapon (other than a shotgun or a shotgun shell which the Secretary
finds is generally recognized as particularly suitable for sporting purposes) by
whatever name known which will, or which may be readily converted to, expel a
projectile by the action of an explosive or other propellant, and which has any barrel
with a bore of more than one-half inch in diameter; and
(C) any combination of parts either designed or intended for use in converting any
device into any destructive device described in subparagraph (A) or (B) and from
which a destructive device may be readily assembled.
The Attorney General also has authority to request military assistance in enforcing
the prohibition of transactions involving nuclear materials, 18 U.S.C. § 831. Section 831
proscribes, inter alia, the intentional unauthorized receipt, possession, use, transfer,
alteration, disposal or dispersal of any nuclear material or nuclear byproduct material that
the defendant knows is likely to cause the death or serious bodily injury to any person, or
substantial damage to property or to the environment. The Attorney General may ask the
Secretary of Defense for the assistance of any DoD personnel in accordance with chapter
18 of title 10, 18 U.S.C. § 831(d), or, in case of an emergency as determined by the
Attorney General and Secretary of Defense, may request military assistance
“notwithstanding [the Posse Comitatus Act].” Assistance under § 831 (probably meaning
subsection (e) only) includes the authority to arrest persons and conduct searches and
seizures, as well as “such other activity as is incidental to” its enforcement or to protect
persons or property from the proscribed conduct. 18 U.S.C. § 831(e). The Secretary of
Defense may require reimbursement as a condition of assistance, 18 U.S.C. § 831(e)(4).
(This last provision should probably be read to apply only to assistance under subsection
(e); reimbursement of assistance under subsection (d) is likely meant to be controlled by
10 U.S.C. § 377.)
There is additional statutory authority, until September 30, 2004, for the Secretary
of Defense to provide assistance to federal law enforcement agencies in responding to acts
or threats of terrorism, 10 U.S.C. § 382 note. The nature of the assistance is not limited
to the operation of equipment, but military personnel may not participate directly in

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searches, seizures, arrests, or “other similar activity,” or the collection of intelligence for
law enforcement purposes. Reimbursement of the incremental costs of providing the
assistance is required but may be waived if the Secretary of Defense determines and
notifies Congress that a waiver is in the interest of national security.
Finally, it is arguable that Congress’ authorization for the use of force against
terrorists responsible for the September 11 attacks, Pub. L. No. 107-40, 115 Stat. 224
(2001), has mooted some of the limitations on the use of the military for law enforcement
purposes by recasting them as military operations. For example, the arrest and rendition
of terrorist suspects abroad for trial in the United States has been unnecessary, as such
persons have instead been transported to the military detention facilities at Guantanamo
Bay, Cuba, where they may eventually be tried by military commissions. By treating
suspected terrorists as “enemy combatants” rather than criminals, the Administration
could assert that their treatment is a matter for the military rather than law enforcement
agencies, even for persons found within the territory of the United States. See Padilla ex
rel. Newman v. Bush, 233 F.Supp.2d 564, 588 (S.D.N.Y. 2002), rev’d in part 352 F.3d
695 (2d Cir. 2003); see also CRS Report RL31724, Detention of American Citizens as
Enemy Combatants.
Inherent Presidential Authority to Use Troops to Enforce the Law
The questions of the President’s authority to act in the absence of an explicit
statutory exception remain unresolved. The PCA aside, it appears that the President may
not use the military to:
! seize an industry critical to national security even in a national
emergency when Congress has declined to empower him to do so,
Youngstown Co. v. Sawyer, 343 U.S. 579 (1952)
! subject civilians to military tribunals for criminal prosecution while
civilian courts remain available, Reid v. Covert, 354 U.S. 1 (1957); Ex
parte Milligan, 71 U.S. (4 Wall.) 2 (1866)

! compel state officials to execute federal authority, Printz v. United States,
521 U.S. 898 (1997).
Restrictions on use of the National Guard (until federalized) are a matter of state law
which varies from jurisdiction to jurisdiction.
Performance in excess of authority might result in criminal and/or civil liability for
responsible officials, 18 U.S.C. § 1385, Bivens v. Six Unknown Agents, 403 U.S. 388
(1971), U.S.Const. Art.II, §4; suppression of evidence, cf., United States v. Walden, 490
F.2d 372 (4th Cir. 1974); dismissed criminal charges and/or reversed convictions, United
States v. Banks, 383 F.Supp. 368 (D.S.D. 1974); United States v. Jaramillo, 380 F.Supp.
1375 (D.Neb. 1974).

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