10 USC 514 - Bounties prohibited; substitutes prohibited

(a) No bounty may be paid to induce any person to enlist in an armed force. A clothing allowance or enlistment bonus authorized by law is not a bounty for the purposes of this subsection.
(b) No person liable for active duty in an armed force under this subtitle may furnish a substitute for that active duty. No person may be enlisted or appointed in an armed force as a substitute for another person.