Also... via https://www.sss.gov/register/who-needs-to-register/
"Immigrants & Dual Nationals:
U.S. immigrants are required by law to register with the Selective Service System 30 days after their 18th birthday or 30 days after entry into the United States if they are between the ages of 18 and 25. This includes U.S. born and naturalized citizens, parolees, undocumented immigrants, legal permanent residents, asylum seekers, refugees, and all males with visas of any kind which expired more than 30 days ago."