Do you have to register your son who has a developmental disability with the Selective Service?  The answer is, Yes. 

 

From the Selective Service Systems Website:

 

Does a student’s disability preclude the requirement to register?

Men with disabilities that would disqualify them from military service still must register with Selective Service. Selective Service does not presently have authority to classify men, so even men with obvious handicaps must register now. Classifications would only be established if a draft were reinstated. 

 

Source: https://www.sss.gov/QA

 

http://autism.about.com/od/transitioncollegejobs/f/selectiveservic.htm