10 U.S.C. § 12315 — Reserves: duty with or without pay

(a) A Reserve can be ordered to active duty or other duty. They can either (1) receive the pay and allowances the law provides, or (2) serve without pay, but only if they agree to it. If a Reserve serves without pay, that service still counts as if it were paid duty for every other purpose, like retirement credit. (b) Sometimes a Reserve stays on active duty even after their service commitment has technically ended. That Reserve is still entitled to pay and allowances during that extra time. There are three exceptions: if a court-martial takes away the pay as part of a sentence, if a commanding officer takes it away through non-judicial punishment, or if the Reserve is otherwise not eligible for pay for some other reason.