Males living in the United States between the ages of 18 and 26, including naturalization applicants, must register for the Selective Service. While failure to register for the Selective Service is not a statutory or regulatory bar, it may still stop a person from naturalizing. This practice advisory will look deeper into the Selective Service requirements, how USCIS will evaluate the case depending on the good moral character time period, and discuss possible strategies for overcoming a failure to register.