Received the photo above along with this explanation from Irregular Mark from New York.
This picture was taken at the main entrance to the Rochester, NY Gun Show, put on by the “Empire State Arms Collector’s Association” (esaca). I mentioned that there was no such federal law and had some of the dealers there argue with me about it. They not only claimed there was such a requirement, but were supportive of it and claimed I’d be in “big trouble” if I made a private sale without a background check. I suspect they just wanted folks making a private transaction to come over and pay them an FFL fee for the privilege of selling their private property to another private citizen. Shameful.