8 CFR §315.1

As used in this part: Exemption from military service means either: Induction means compulsory entrance into military service of the United States whether by conscription or, after being notified of a pending conscription, by enlistment. Treaty national means an alien who is a national of a country with which the United States has a treaty relating to the reciprocal exemption of aliens from military training or military service.

(1) A permanent exemption from induction into the Armed Forces or the National Security Training Corps of the United States for military training or military service; or

(2) The release or discharge from military training or military service in the Armed Forces or in the National Security Training Corps of the United States.