 Today, non-citizen males of appropriate age in the United States, who are permanent residents (holders of green cards), seasonal agricultural workers not holding an H-2A Visa, refugees, parolees, asylees, and illegal immigrants, are required to register with the Selective Service System.Refusal to do so is grounds for denial of a future citizenship application.In addition, immigrants who seek to naturalize as citizens must, as part of the Oath of Citizenship, swear to the following