10 U.S.C. § 8146

(a) Under such regulations as he may prescribe, the Secretary of the Navy may make temporary appointments of officers designated for limited duty in the Regular Navy in grades not above lieutenant and in the Regular Marine Corps in grades not above captain from sources authorized under section 8139 of this title . Such appointments shall be made by warrant if in the grade of warrant officer, W–1, and by commission if in a higher grade. (b) Temporary appointments under this section do not change the permanent, probationary, or acting status of members so appointed, prejudice them in regard to promotion or appointment, or abridge their rights or benefits. A person receiving a temporary appointment under this section may not suffer any reduction in the pay and allowances to which he was entitled because of his permanent status at the time of his temporary appointment, or any reduction in the pay and allowances to which he was entitled under a prior temporary appointment in a lower grade. (c) The following members of the naval service are ineligible for temporary appointments under this section: (1) Retired members. (2) Members of the Navy Reserve and the Marine Corps Reserve ordered to active duty for training. (3) Members of the Navy Reserve and the Marine Corps Reserve ordered to active duty in connection with organizing, administering, recruiting, instructing, training, or drilling the Navy Reserve or the Marine Corps Reserve. (4) Members of the Navy Reserve and the Marine Corps Reserve ordered to temporary active duty to prosecute special work. (d) Officers designated for limited duty under subsection (a) may be temporarily appointed by the Secretary of the Navy in a higher grade not above commander in the Regular Navy or lieutenant colonel in the Regular Marine Corps under such regulations as the Secretary may prescribe. Regulations prescribed under this section shall to the greatest extent practicable conform to the procedures prescribed in chapter 36 of this title for selection for promotion and promotion to higher permanent grades. (e) The Secretary of the Navy may terminate any appointment made under this section.