Devil is in the detail. The EU wants to protect itself from cheap imports being white labelled in the UK a perfectly reasonable position. How they achieve that goal is probably not in the treaty.

As I have said before if the EU wanted to play nice it could offer a preferred trader scheme to the major companies so instead of inspecting every single shipment the trader promises to obey EU rules with stiff fines if they don't. The likes of M&S are not going to risk being caught.