10 U.S.C. § 531

(a) (1) Original appointments in the grades of second lieutenant, first lieutenant, and captain in the Regular Army, Regular Air Force, Regular Marine Corps, and Space Force, and in the grades of ensign, lieutenant (junior grade), and lieutenant in the Regular Navy shall be made by the President alone. (2) Original appointments in the grades of major, lieutenant colonel, and colonel in the Regular Army, Regular Air Force, Regular Marine Corps, and Space Force, and in the grades of lieutenant commander, commander, and captain in the Regular Navy shall be made by the President, by and with the advice and consent of the Senate. (b) The grade of a person receiving an appointment under this section who at the time of appointment (1) is credited with service under section 533 of this title , and (2) is not a commissioned officer of a reserve component shall be determined under regulations prescribed by the Secretary of Defense based upon the amount of service credited. The grade of a person receiving an appointment under this section who at the time of the appointment is a commissioned officer of a reserve component is determined under section 533(f) of this title . (c) Subject to the authority, direction, and control of the President, an original appointment as a commissioned officer in the Regular Army, Regular Air Force, Regular Navy, Regular Marine Corps, or Space Force may be made by the Secretary of Defense in the case of a reserve commissioned officer upon the transfer of such officer from the reserve active-status list of a reserve component of the armed forces to the active-duty list of an armed force, notwithstanding the requirements of subsection (a).