Have him register, there's literally zero harm in him doing so. As a former military member and father of current military members as well as an adult son with Asperger's, even in the extremely unlikely event that the draft was reinstated anyone who has been diagnosed with any of the autism spectrum disorders and/or is on medication to treat any of those or ADD/ADHD wouldn't pass the physical evaluation to enter military service. So, no need to worry about him signing up for selective service 👍🏼

How my son just turned 18 December 9. I would like to say thank you because I didn’t think about that since he has Autism but I did look up on something at sss.gov hopefully this site will help

You welcome

Thank you