netsecurity
Shooter
How would they know whether or not I actually did the background check without registration?
Well at a gun show they could monitor private sales. Outside the gun shows I do not think it would be enforceable, but I think background checks should be freely available if they are required.
The real problem is that if they make NICS freely available to all individuals then it would be abused. Fathers would want to call in to check on their daughter's boyfriend, employers would use it for a free background check, etc.