(a) Any commissioned officer on active duty is eligible to serve on all courts-martial for the trial of any person who may lawfully be brought before such courts for trial.
(b) Any warrant officer on active duty is eligible to serve on general and special courts-martial for the trial of any person, other than a commissioned officer, who may lawfully be brought before such courts for trial.
(1) Any enlisted member of an armed force on active duty who is not a member of the same unit as the accused is eligible to serve on general and special courts-martial for the trial of any enlisted member of an armed force who may lawfully be brought before such courts for trial, but he shall serve as a member of a court only if, before the conclusion of a session called by the military judge under section 839(a) of this title (article 39(a)) prior to trial or, in the absence of such a session, before the court is assembled for the trial of the accused, the accused personally has requested orally on the record or in writing that enlisted members serve on it. After such a request, the accused may not be tried by a general or special courts-martial the membership of which does not include enlisted members in a number comprising at least one-third of the total membership of the court, unless eligible enlisted members cannot be obtained on account of physical conditions or military exigencies. If such members cannot be obtained, the court may be assembled and the trial held without them, but the convening authority shall make a detailed written statement, to be appended to the record, stating why they could not be obtained.
(2) In this article, “unit” means any regularly organized body as defined by the Secretary concerned, but in no case may it be a body larger than a company, squadron, ship’s crew, or body corresponding to one of them.
(1) When it can be avoided, no member of an armed force may be tried by a court-martial any member of which is junior to him in rank or grade.
(2) When convening a court-martial, the convening authority shall detail as member thereof such members of the armed forces as, in his opinion, are best qualified for the duty by reason of age, education, training, experience, length of service, and judicial temperament. No member of an armed force is eligible to serve as a member of a general or special court-martial when he is the accuser or a witness for the prosecution or has acted as investigating officer or as counsel in the same case.
(e) Before a court-martial is assembled for the trial of a case, the convening authority may excuse a member of the court from participating in the case. Under such regulations as the Secretary concerned may prescribe, the convening authority may delegate his authority under this subsection to his staff judge advocate or legal officer or to any other principal assistant.