5 U.S.C. § 3361

(a) In General .— An individual may be promoted in the competitive service only if he has passed an examination or is specifically excepted from examination under section 3302 of this title . This section does not take from the President any authority conferred by section 3301 of this title that is consistent with the provisions of this title governing the competitive service. (b) DOD Promotions .— Promotions in the competitive service within the Department of Defense may be made based on demonstrated skills and qualifications without regard to minimum time-in-grade requirements, subject to agency policies and applicable merit system principles.