Two holes are apparent:
1) A ban on selling handguns would certainly be overturned by the current SCOTUS court, and quickly.
2) The litigant would have to get a win on the suit, and that is certainly no lock.
Not if you can't sue the state because the state's not the one enforcing the law. You won't ever get SCOTUS to consider the case.
That's exactly the state of play with the TX law right now.
I don't think it will last but the whole point of this tactic is to keep the issue away from SCOTUS.