All 50 states have a different procedure for restoring rights. Some refuse to do so or make it impossibly difficult, others automatically restore them after 5 or 10 years.
Vermont was the only state not to strip ex offenders of rights. The ATF position was: "Well, technically, if those rights were never taken away THEY WEREN'T RESTORED, so we're arresting you for felon in possession of a firearm federally even though you're legal under state law."