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.
Whenever the President considers that unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States, make it impracticable to enforce the laws of the United States in any State by the ordinary course of judicial proceedings, he may call into Federal service such of the militia of any State, and use such of the armed forces, as he considers necessary to enforce those laws or to suppress the rebellion.
18 U.S.C. § 592, Troops at Polls.
Whoever, being an officer of the Army or Navy, or other person in the civil, military, or naval service of the United States, orders, brings, keeps, or has under his authority or control any troops or armed men at any place where a general or special election is held, unless such force be necessary to repel armed enemies of the United States, shall be fined under this title or imprisoned not more than five years, or both; and be disqualified from holding any office of honor, profit, or trust under the United States.
18 U.S.C. § 593, Interference by armed forces.
Whoever, being an officer or member of the Armed Forces of the United States, prescribes or fixes or attempts to prescribe or fix, whether by proclamation, order or otherwise, the qualifications of voters at any election in any State; or
Whoever, being such officer or member, prevents or attempts to prevent by force, threat, intimidation, advice or otherwise any qualified voter of any State from fully exercising the right of suffrage at any general or special election; or
Whoever, being such officer or member, orders or compels or attempts to compel any election officer in any State to receive a vote from a person not legally qualified to vote; or
Whoever, being such officer or member, imposes or attempts to impose any regulations for conducting any general or special election in a State, different from those prescribed by law; or
Whoever, being such officer or member, interferes in any manner with an election officer’s discharge of his duties—
Shall be fined under this title or imprisoned not more than five years, or both; and disqualified from holding any office of honor, profit or trust under the United States.
This section shall not prevent any officer or member of the Armed Forces from exercising the right of suffrage in any district to which he may belong, if otherwise qualified according to the laws of the State of such district.
18 U.S.C. § 594, Intimidation of voters
Whoever intimidates, threatens, coerces, or attempts to intimidate, threaten, or coerce, any other person for the purpose of interfering with the right of such other person to vote or to vote as he may choose, or of causing such other person to vote for, or not to vote for, any candidate for the office of President, Vice President, Presidential elector, Member of the Senate, Member of the House of Representatives, Delegate from the District of Columbia, or Resident Commissioner, at any election held solely or in part for the purpose of electing such candidate, shall be fined under this title or imprisoned not more than one year, or both.