((a)) The following persons are exempt from militia duty:

((1)) The Vice President.

((2)) The judicial and executive officers of the United States, the several States, the Commonwealth of Puerto Rico, Guam, and the Virgin Islands.

((3)) Members of the armed forces, except members who are not on active duty.

((4)) Customhouse clerks.

((5)) Persons employed by the United States in the transmission of mail.

((6)) Workmen employed in armories, arsenals, and naval shipyards of the United States.

((7)) Pilots on navigable waters.

((8)) Mariners in the sea service of a citizen of, or a merchant in, the United States.

((b)) A person who claims exemption because of religious belief is exempt from militia duty in a combatant capacity, if the conscientious holding of that belief is established under such regulations as the President may prescribe. However, such a person is not exempt from militia duty that the President determines to be noncombatant.