When reading the "POTUS Changes his mind on AWB" thread the thought came to me that a universal background check law would be unenforceable. Think about it, if you were going to sell a gun you bought say in the 70's to your neighbor would you run a background check? The gun isn't on anybody's books as it was bought before background checks were required and you know your neighbor. I just don't see how it could be enforceable.