In the US state of Delaware, we have instant background checks with a single phone call, and nearly all transfers of weapons are contingent on the background check. So, no “gun show loophole”, although we do have the “cop loophole” (which nobody cares about but me).
Also in Delaware, you can (and people do) sell homemade beer and cider at a flea markets and yard sales, because the police have decided to turn a blind eye to federal laws about homebrewing. You can’t openly sell kegs or unlicensed hard liquor, though, and the blind eye of the police will suddenly become all-seeing if you try to sell alcohol to a minor.
I want to say originally it was purely a state initiative, but now tied into the national system run through the FBI, and also into the systems of the surrounding states. But don’t trust that! I don’t really know!
I would consult my expert but Pedro is currently in Italy.
I just looked it up, and Delaware uses the same NICS system that all federally licensed dealers use. Additionally, they require private individuals transferring or selling a gun to locate a licensed dealer to conduct a federal check before a transfer can take place.