There are very few exemptions from registration. If a man is serving on active duty in the Armed Forces prior to reaching the age of 18, he does not have to register upon reaching the age of 18; however, if he leaves active duty prior to reaching age 26, he must timely register after his discharge from active duty. Those attending a U.S. Service Academy or certain other U.S. military colleges are also exempt so long as they remain enrolled in the academy or on active duty status; such men must register upon withdrawing from the academy or leaving active duty service. Non-immigrant non-citizens in the U.S. on student, visitor, tourist or diplomatic visas are also exempt from registration. A man who is confined to a home for medical reasons (and unable to leave without medical assistance), or placed in a hospital, nursing home, long-term care facility or mental institution, prior to his 18th birthday is exempt from registration for so long as the homebound confinement or institutional placement continues.