What does PCA mean in Military?

Posse Comitatus Act

The Posse Comitatus Act is a United States federal law (18 U.S.C. § 1385, original at 20 Stat. 152) signed on June 18, 1878, by President Rutherford B. Hayes which limits the powers of the federal government in the use of federal military personnel to enforce domestic policies within the United States. Congress passed the Act as an amendment to an army appropriation bill following the end of Reconstruction and updated it in 1956 and 1981. The Act originally applied only to the United States Army, but a subsequent amendment in 1956 expanded its scope to the United States Air Force. In 2021, the National Defense Authorization Act for Fiscal Year 2022 further expanded the scope of the Act to cover the United States Navy, Marine Corps, and Space Force. The Act does not prevent the Army National Guard or the Air National Guard under state authority from acting in a law enforcement capacity within its home state or in an adjacent state if invited by that state's governor. The United States Coast Guard (under the Department of Homeland Security) is not covered by the Act either, primarily because although it is a armed service, it also has a maritime law enforcement mission. The title of the Act comes from the legal concept of posse comitatus, the authority under which a county sheriff, or another law officer, can conscript any able-bodied person to assist in keeping the peace.

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