18 U.S.C. § 609

Whoever, being a commissioned, noncommissioned, warrant, or petty officer of an Armed Force, uses military authority to influence the vote of a member of the Armed Forces or to require a member of the Armed Forces to march to a polling place, or attempts to do so, shall be fined in accordance with this title or imprisoned not more than five years, or both. Nothing in this section shall prohibit free discussion of political issues or candidates for public office.