Congressional Research Service ˜ The Library of Congress
CRS Report for Congress
Received through the CRS Web
Order Code RS21012
Updated May 27, 2005
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 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. Further exceptions are proposed (H.R. 1986,
H.R. 1815). 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 and
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
