We already have that law. It covers that subset of paranoid schizophrenics who have gone before a judge and been -adjudicated- mentally defective due to being a demonstrable risk to themselves or others. They retain the right of appeal of that finding and can get their rights back. 

That's the key, no denial of individual rights without individual due process. That's the problem with the Dems blanket "no fly, no buy" legislation nonsense. Zero due process to be put on, and zero appeal available.