because those specific guns as identified by those certificates are deemed to still be Non-Restricted... but... the moment someone tries to sell or transfer one of those guns, the instant the Transfer Request is entered into the CFC system then the gun becomes frozen... it instantly at that point becomes a "Prohibited" firearms as per the new classification and at that point it's trapped... it can't be transferred and it can't be cancelled back to the old owner because it's now a Prohib and the old owner can't possess it (no-one can... at least no individual can). And so those few specific guns remain out there.