(a) Each classified registrant in a selection group is available for unrestricted military service until his eligibility for noncombatant service, alternative service, or deferment or exemption from service has been determined by a classifying authority.

(b) The classifying authority in considering a registrant's claim for classification shall not discriminate for or against him because of his race, creed, color or ethnic background and shall not discriminate for or against him because of his membership or activity in any labor, political, religious, or other organization.