The Posse Comitatus Act is a United States federal law (18 U.S.C. Â§ 1385) passed on June 18, 1878, after the end of Reconstruction, with the intention (in concert with the Insurrection Act of 1807) of substantially limiting the powers of the federal government to use the military for law enforcement. The Act prohibits most members of the federal uniformed services (today the Army, Navy, Air Force, and State National Guard forces when such are called into federal service) from exercising nominally state law enforcement, police, or peace officer powers that maintain law and order on non-federal property (states and their counties and municipal divisions) within the United States.