(a) All registrants available for unrestricted military service shall be in Class 1-A.

(b) All registrants in the selection groups as determined by the Director of Selective Service are available for unrestricted Military Service, except those determined by a classifying authority to be eligible for exemption or deferment from military service or for noncombatant or alternative service, or who have random sequence numbers (RSNs) determined by the Director not to be required to fill calls by the Secretary of Defense.