From Wikipee, who's rarely unbiased, but in this case managed some basic facts (Infogalactic is better):
"Under current law, all male U.S. citizens between 18–25 (inclusive) years of age are required to register within 30 days of their 18th birthday. In addition, certain categories of non-US citizen men between 18–25 living in the United States must register, particularly permanent residents, refugees, asylum seekers, and illegal immigrants.[2]"~~
The illegals better run. I need popcorn for the Demorrhoid reaction.