10 U.S.C. § 15104

(a) Specification of Number of Opportunities for Consideration for Promotion .— In designating a competitive category of officers pursuant to section 15101 of this title , the Secretary of a military department shall specify the number of opportunities for consideration for promotion to be afforded officers of the armed force concerned within the category for promotion to each grade above the grade of first lieutenant or lieutenant (junior grade), as applicable. (b) Limited Authority of Secretary of Military Department to Modify Number of Opportunities .— The Secretary of a military department may modify the number of opportunities for consideration for promotion to be afforded officers of an armed force within a competitive category for promotion to a particular grade, as previously specified by the Secretary pursuant subsection (a) of this subsection, not more frequently than once every five years. (c) Discretionary Authority of Secretary of Defense to Modify Number of Opportunities .— The Secretary of Defense may modify the number of opportunities for consideration for promotion to be afforded officers of an armed force within a competitive category for promotion to a particular grade, as previously specified or modified pursuant to any provision of this section, at the discretion of the Secretary. (d) Limitation on Number of Opportunities Specified .— The number of opportunities for consideration for promotion to be afforded officers of an armed force within a competitive category for promotion to a particular grade, as specified or modified pursuant to any provision of this section, may not exceed five opportunities. (e) Effect of Certain Reduction in Number of Opportunities Specified .— If, by reason of a reduction in the number of opportunities for consideration for promotion under this section, an officer would no longer have one or more opportunities for consideration for promotion that were available to the officer before the reduction, the officer shall be afforded one additional opportunity for consideration for promotion after the reduction.