We'll have to for at least one year. Anyone trading within the EU will have to comply beyond, but those only trading within the UK might kick up a stink and try and get it moved up the the pile of things to revoke once the split is done. Unless she delivers a fake Brexit of course - AKA Soft Brexit. Although any government with the power to vapourise businesses at will will probably enjoy it too much to relinquish. She's supposed to be quite authoritarian by impulse.