18 U.S.C. § 1385—Posse Comitatus Act.
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.
10 U.S.C. § 252—(Insurrection Act) Use of militia and armed forces to enforce Federal authority.