Posse Commitatus Act 18 U.S.C. § 1385

Sec. 1385. - Use of Army and Air Force as posse comitatus

"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".

This federal statute places strict limits on the use of military personnel for law enforcement. Enacted in 1878, the PCA prohibits the willful use of the US Army (and later, the US Air Force for law enforcement duties, except as authorized by the President, Congress or the US Constitution, or in certain emergency situations. Although the PCA, by its terms, refers only to the Army and Air Force, DOD policy extends the prohibitions of the Act to US Navy and Marine Corps forces, as well.

Specifically prohibited activities include: interdiction of a vehicle, vessel, aircraft, or similar activity; search and/or seizure; arrest, apprehension, “stop-andfrisk” detentions, and similar activities; and use of military personnel for surveillance or pursuit of individuals, or as undercover agents, informants, investigators, or interrogators. DODD 5525.5, DOD Cooperation with Civilian Law Enforcement Officials, sets forth several forms of assistance civilian authorities, which are allowed under the PCA. Exceptions to PCA include:

  • National Guard forces while under the authority of the governor of a state or Title 32;
  • Federal troops acting pursuant to the presidential power Federal authority to quell domestic violence (Ex. 1992 Los Angeles riots);
  • Troops used under the order of the President of the United States pursuant to the Insurrection Act;
  • Aerial photographic and visual search and surveillance by military;
  • Congressionally created “drug exception.”;
  • The USCG when operating under Title 14 authority;
  • Under 18 U.S.C. § 831, the Attorney General may request that the Secretary of Defense provide emergency assistance if civilian law enforcement is inadequate to address certain types of threat involving the release of nuclear materials, such as potential use of a Nuclear or Radiological weapon. Such assistance may be by any personnel under the authority of the Department of Defense, provided such assistance does not adversely affect U.S. military preparedness.