10 U.S.C. § 143: Office of the Secretary of Defense personnel: limitation

The number of OSD personnel may not exceed 4,300. For purposes of this section, the term “OSD personnel” means military and civilian personnel of the Department of Defense who are assigned to, or employed in, functions in the Office of the Secretary of Defense (including Direct Support Activities of that Office and the Washington Headquarters Services of the Department of Defense). In carrying out reductions in the number of personnel assigned to, or employed in, the Office of the Secretary of Defense in order to comply with this section, the Secretary of Defense may not reassign functions solely in order to evade the requirements contained in this section. acquisition personnel hired pursuant to the expedited hiring authority provided in section 1705(h) [now 1705(g)] of title 10, United States Code, as amended by section 833 of this Act, or otherwise hired with funds in the Department of Defense Acquisition Workforce Development Fund established in accordance with section 1705(a) of such title; or personnel hired pursuant to a shortage category designation by the Secretary of Defense or the Director of the Office of Personnel Management. fill a gap in the civilian workforce of the Department of Defense identified by the Secretary of Defense in a strategic human capital plan submitted to Congress in accordance with the requirements of [former] section 115b of such title; or Performance of inherently governmental functions. Performance of work pursuant to section 2463 of title 10 , United States Code. Ability to maintain sufficient organic expertise and technical capability. Performance of work that, while the position may not exercise an inherently governmental function, nevertheless should be performed only by officers or employees of the Federal Government or members of the Armed Forces because of the critical nature of the work.”