10 U.S.C. § 603

1. (a)In time of war, or of national emergency declared by the Congress or the President after November 30, 1980, the President may appoint any qualified person (whether or not already a member of the armed forces) to any officer grade in the Army, Navy, Air Force, Marine Corps, or Space Force, except that appointments under this section may not be made in grades above major general or rear admiral. Appointments under this section shall be made by the President alone, except that an appointment in the grade warrant officer, W–1, shall be made by warrant by the Secretary concerned.
2. (b)Any appointment under this section is a temporary appointment and may be vacated by the President at any time.
3. (c)
   1. (1)Any person receiving an original appointment under this section is entitled to service credit as authorized under section 533 of this title.
   2. (2)An appointment under this section of a person who is not on active duty becomes effective when that person begins active duty under that appointment.
4. (d)An appointment under this section does not change the permanent status of a member of the armed forces so appointed. A member who is appointed under this section shall not incur any reduction in the pay and allowances to which the member was entitled, by virtue of his permanent status, at the time of his appointment under this section.
5. (e)
   1. (1)An officer who receives an appointment to a higher grade under this section is considered to have accepted such appointment on the date of the order announcing the appointment unless he expressly declines the appointment.
   2. (2)An officer who has served continuously since he subscribed to the oath of office prescribed in section 3331 of title 5 is not required to take a new oath upon appointment to a higher grade under this section.
6. (f)Unless sooner terminated, an appointment under this section terminates on the earliest of the following:
   1. (1)The second anniversary of the appointment.
   2. (2)The end of the six-month period beginning on the last day of the war or national emergency during which the appointment was made.
   3. (3)The date the person appointed is released from active duty.