Hard to comment without specific legislation proposed yet, but I'd think that the enforcement would come at place of purchase.
Now if you have a gun, they could ask where and when you got it. But I'm thinking the seller is the one who could potentially get in trouble, not someone with a gun.
The feds know about every one of my guns, and personally I don't mind. But I've got nothing to hide, and I welcome police and military friends over to my house.
G19 G26 G30 Sig 2340 357 Beretta U22 (kid's) Two Saiga 12 Two Draco 7.62x39 "pistols" Colt 6920 Saiga SGL21-94, M92 Krinkov "pistol," PSA Patrol Carbine Saiga 223 CCDW KY