If the court has handed down a sentence and I complete that sentence (time served, parole, etc), I have "paid my debt to society" and it would (or maybe I should say "should") take another hearing or trial in order to restrict my rights. In fact, if I remember correctly, there is even case law on something similar.
As I have said, if it is not safe for someone to be in society with their full rights, then do not let them back into society. But once a sentence is carried out and completed, you have said, in effect, it is safe for this person to return to his place in society. Once that is done, why should he be denied the right to self protection afforded any other member of society?
And besides, as I said in a post above, what good does it do? They can get guns anyway, and you end up using the same arguments the gun grabbers use, gun control to keep guns out of the hands of the bad guys.
Ok, he is an ex-felon and you have denied him his rights. He buys a gun, is caught and is back in jail. Why not just keep him in there to begin with if you have deemed him unsafe to fit back into society without his full rights restored?
It would be nice if any of this were true, but it isn't. The existing law is the rule, not what we'd like the law to be. If the law is (as it is in Missouri) that felons can't have guns that's the way it is. As for "paying a debt to society" -- that ain't law either. The phrase is used all the time but it has no basis in law.