Ok, I'm going to blow that law straight ta Hell. I actually have a Tac-1 Carbine (made by Demro) that fires from an open bolt. Pre-'86. Semi-auto. Loaded magazine inserted into the gun. No round chambered. Trigger holds the entire bolt back. Fixed firing pin on the bolt. A round is ONLY chambered just before it goes "BANG". It only takes a single pull of the trigger to make it chamber a round and then immediately fire.
So, under that law, I can carry any open-bolt gun, ready to fire, but it would be considered "unloaded".