Registration would have to be required period, not at the time of sale. Then you would be unable to transfer a gun not registered after the registry is closed.I am NOT advocating for universal background checks, but I disagree that it would mean having to create a gun registry. I think they will push for one, but it doesnt have to create one. People can still lie about having a gun for years even if registration is required at the time of the sell. I think that their end goal is a registry and probably a ban of some sort though.
As GP said, without the registry there is no way to enforce UBCs. They have been tried and failed in many places in the past, including here in Indiana.