10 U.S.C. § 12408

(a) Under regulations prescribed by the President, each member of the National Guard called into Federal service under section 12301(a), 12302, or 12304 of this title shall be examined as to physical fitness, without further commission or enlistment. (b) Immediately before such a member is mustered out of Federal service, he shall be examined as to physical fitness. The record of this examination shall be retained by the United States.