My best friend is going through this right now. In his teens he did a lot of drugs. And like most addicts went into business in "Urban Pharmaceutical Distribution" to support his habit. LEO had their eye on him and waited until he turned 18 to make an arrest (about a month after his b-day). Diversion was denied by the judge and he served 9 months of a 3 year sentence.
More than 10 years later he is trying to get his rights reinstated. Not looking good. Crazy thing is he is an IT security auditor for banks. He can be trusted to hack into banks and do physical vulnerability assessments, but can't own a gun, pure silliness.
Once you have paid your debt, you should be granted your full citizenship rights back. If you can't trust them to be out on the street, don't let them out in the first place. Don't mistake me for some bleeding heart, soft on crime type. I am all for eliminating parole mixed with longer sentences in less hospitable accommodations, but when the sentence is over the debt should be stamped "paid in full".