14 USC 332 - Recall to active duty with consent of officer

(a) Any regular officer on the retired list may, with that officers consent, be assigned to such duties as that officer may be able to perform.
(b) The number of retired officers on active duty in the grade of lieutenant commander, commander, or captain shall not exceed 2 percent of the authorized number of officers on active duty in each such grade. However, this limitation does not apply to retired officers of these grades recalled to serve as members of courts, boards, panels, surveys, or special projects for periods not to exceed one year.