10 U.S.C. § 12313: Reserves: release from active duty

(a) Except as otherwise provided in this title, the Secretary concerned may at any time release a Reserve under his jurisdiction from active duty. (b) In time of war or of national emergency declared by Congress or the President after January 1, 1953, a member of a reserve component may be released from active duty (other than for training) only if—(1) a board of officers convened at his request by an authority designated by the Secretary concerned recommends the release and the recommendation is approved; (2) the member does not request that a board be convened; or (3) his release is otherwise authorized by law. This subsection does not apply to an armed force during a period of demobilization or reduction in strength of that armed force.