to provide legal assistance with respect to any proceeding or litigation arising out of a violation of the Military Selective Service Act [
50 U.S.C. 3801 et seq.] or of desertion from the Armed Forces of the United States, except that legal assistance may be provided to an eligible client in a civil action in which such client alleges that he was improperly classified prior to
July 1, 1973, under the Military Selective Service Act or prior corresponding law; or