10 U.S.C. § 14102

(a) Appointment .— Members of selection boards convened under section 14101 of this title shall be appointed by the Secretary of the military department concerned in accordance with this section. Promotion boards and special selection boards shall consist of five or more officers. Selection boards convened under section 14101(b) of this title shall consist of three or more officers. All of the officers of any such selection board shall be of the same armed force as the officers under consideration by the board. (b) Composition .— At least one-half of the members of such a selection board shall be reserve officers, to include at least one reserve officer from each reserve component from which officers are to be considered by the board. Each member of a selection board must hold a permanent grade higher than the grade of the officers under consideration by the board, and no member of a board may hold a grade below major or lieutenant commander. The members of a selection board shall represent the diverse population of the armed force concerned to the extent practicable. (c) Representation of Competitive Categories .— (1) Except as provided in paragraph (2), a selection board shall include at least one officer from each competitive category of officers to be considered by the board. (2) A selection board need not include an officer from a competitive category to be considered by the board if there is no officer of that competitive category on the reserve active-status list or the active-duty list in a permanent grade higher than the grade of the officers to be considered by the board and otherwise eligible to serve on the board. However, in such a case, the Secretary of the military department concerned, in his discretion, may appoint as a member of the board a retired officer of that competitive category who is in the same armed force as the officers under consideration by the board who holds a higher grade than the grade of the officers under consideration. (d) Prohibition of Service on Consecutive Promotion Boards .— No officer may be a member of two successive promotion boards convened under section 14101(a) of this title for the consideration of officers of the same competitive category and grade if the second of the two boards is to consider any officer who was considered and not recommended for promotion to the next higher grade by the first of the two boards.