I know some of the newer Benellis have a notch on the bottom of the bolt or carrier that prevents this, so I guess they got the word. I have done a little scouting around, and it appears some wardens already know about this and are checking. None of my guns will do it, and I am not into tactical so I was oblivious. It appears several brands of pumps and semi autos can do this. I don't know all the state laws, but I know the Federal boys can confiscate your gun - saw it happen in Maryland. Guy had only been loading two in the magazine, but he had forgotten his plug.
If you have a gun that can be ghost loaded, and you plan to waterfowl hunt, or hunt where the capacity is limited by law, I would get in touch with the manufacturer and see if they have a fix they can send you. Losing your gun and getting smacked with a hefty fine would make for a bad day.
I got a $385 fine 20 years ago for one dove over the limit. My dog was retrieving for me and a couple of other guys. I had actually walked back to the truck and unloaded and was sitting there drinking an iced tea when the warden checked me. I have never been more shocked than when he counted the birds. I counted them again, and told him what must have happened. He was very sympathetic as he wrote out the ticket. He said, "You know I could confiscate your gun, too, don't you?" Terror struck me as I glanced at my $5500 SxS 28 gauge. He must have been scared I was going to have a heart attack, because he quickly added he wasn't going to. I have been a wee bit more careful since.