Posse comitatus. A group of citizens who are called together to help the sheriff keep the peace or conduct rescue operations.
Posse Comitatus Act. A federal law that, with a few exceptions, prohibits the Army or Air Force from directly participating in civilian law-enforcement operations, as by making arrests, conducting searches, or seizing evidence. The Act was originally enacted in 1878. It does not usually apply to members of the Navy, the National Guard, or the Coast Guard. 18 USCA § 1385.