The qualifications for enlistment and re-enlistment in the National Guard and the term and the form of oath shall at all times conform to the requirements of the laws of the United States and of this State and the regulations from time to time promulgated by the Department of the Army or the Department of the Air Force of the United States for the government and guidance of the National Guard except for former enlisted members of the United States Army, United States Air Force, United States Navy, or any reserve component thereof, who were honorably separated therefrom but are no longer qualified for enlistment under the laws of the United States.