I don't know what you mean by "surpassed long ago" but I assume you mean GATT 24 although there is no clarity in your point.
The UK is, as are all nations, free to control its borders as it sees fit, including not enforcing them (whatever that might mean). Let me get this straight you think that the EU would confiscate and destroy goods coming from the UK? On what grounds? It would appear that you are suggesting that the EU would treat goods from the UK differently to goods from other nations. Is that what you meant? And how do you propose that this discriminatory customs regime would be enforced?
Oh, go on then. I could do with a laugh.