In English common law, the power of a county sheriff to enlist able-bodied citizens of the county to help him in the pursuit and arrest of a felon.
"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." (Title 18, Section 1385 of the United States Code)
by flood control dam #3 March 22, 2007