14 U.S.C. § 2161: Composition of boards

(a) A board convened under section 2158 or 2159 of this title shall consist of at least three officers of the grade of commander or above, all of whom are serving in a grade senior to the grade of any officer considered by the board. (b) No individual may be a member of more than one board convened under section 2158 or 2159 of this title to consider the same officer.