32 U.S.C. § 503 — Participation in field exercises

(a)(1) Under regulations the President may prescribe, the Secretary of the Army and the Secretary of the Air Force may have the National Guard take part in encampments, maneuvers, outdoor target practice, or other exercises for field or coast-defense instruction — either independently, or together with the Army or the Air Force, or both. (2) This includes joint exercises training the National Guard to respond to civil emergencies and disasters, done alongside the Army or the Air Force, or both. (b) Money needed for the pay, food, transportation, and other proper expenses of any part of the National Guard — from a state, the Commonwealth of Puerto Rico, the District of Columbia, Guam, or the Virgin Islands — taking part in an exercise under subsection (a) may be set aside from funds allocated to it for field or coast-defense instruction. (c) National Guard members taking part in an exercise under subsection (a) may, once mustered, be paid for the whole period from the day they leave home to the day they return, as determined in advance. If that payment turns out to be correct, it is credited to the disbursing officer's account.