33 U.S. Code § 3074 - Commissary privileges
(a) Extension of privilege
Commissioned officers, ships’ officers, and members of crews of vessels of the Administration shall be permitted to purchase commissary and quartermaster supplies as far as available from the Armed Forces at the prices charged officers and enlisted members of the Armed Forces.
(b) Sales of rations, stores, uniforms, and related equipment
The Secretary may purchase ration supplies for messes, stores, uniforms, accouterments, and related equipment for sale aboard ship and shore stations of the Administration to members of the uniformed services and to personnel assigned to such ships or shore stations. Sales shall be in accordance with regulations prescribed by the Secretary, and proceeds therefrom shall, as far as is practicable, fully reimburse the appropriations charged without regard to fiscal year.