It gets back to Justice Thomas' point about a personal RKBA as enumerated in the Second Amendment.
If the RKBA is indeed a personal right as he suggests, can a State infringe that right without violating the Second Amendment?
Yes, because the 2nd amendment doesn't apply to them. These are two completely separate issues you're conflating - how the right is defined by the Constitution, and who's restricted by it from violating that right.