20 CFR § 404.1330 - Who is a member of a uniformed service.
(a) Are appointed, enlisted, or inducted into—
(1) The Air Force, Army, Navy, Coast Guard, or Marine Corps; or
(b) Served in the Army or Air Force under call or conscription;
(c) Are a commissioned officer of the National Oceanic and Atmospheric Administration or its predecessors, the Environmental Science Services Administration and the Coast and Geodetic Survey;
(d) Are a commissioned officer of the Regular or Reserve Corps of the Public Health Service;
(e) Are a retired member of any of the above services;
(f) Are a member of the Fleet Reserve or Fleet Marine Corps Reserve;
(g) Are a cadet at the United States Military Academy, Air Force Academy, or Coast Guard Academy, or a midshipman at the United States Naval Academy; or
(h) Are a member of the Reserve Officers Training Corps of the Army, Navy or Air Force, when ordered to annual training duty for at least 14 days and while performing official travel to and from that duty.