Sebastian at Snow Flakes in Hell has an excellent analysis of this provision. To understand just how radical a bill this is, you must read it. As he notes:
McCarthy’s bill contains no such exemption (as in AWB of 1994 regarding proof of ownership), which puts the burden on you to prove you fall under one of these two exemptions. Carolyn McCarthy has been on NPR saying that the things bloggers have been saying about her bill aren’t true. She knows damned well they are true, and so do the anti-gun groups. The purpose of this bill is to try to get more of us thrown in federal prison.When you have RINO dinosaurs like Dick Lugar coming out in favor of a ban as well as the comments by Dick Cheney, it tells you two things: most don't understand the difference between the law in 1994 and what McCarthy proposes AND we are going to have a fight on our hands to stop this monstrosity.
I am not naive enough to believe that they merely don’t know how to draft laws. Dennis Henigan is not a fool or an idiot. He knows federal guns laws, and I would be very surprised if McCarthy’s staffers didn’t consult with the Brady Center on this bill. By removing the original grandfathering and protections that were in the original 1994 ban, the effect is vastly different than what we lived under with that regime. Under this law, you may really only possess 11 round or greater magazines, unless you have proof you possessed them prior, at the arbitrary discretion of the authorities. How many magazines do you have documentation for?