WTO rules. I was exasperated as fuck whenever I heard a brexit supporter talk their bollocks about unelected EU eurocrats imposing their will on us in an undemocratic way. It was insane as saying Westminster based civil servants impose their rules on us without due democratic process.
The EU protects it's interests with rules we were at the vanguard of implementing when we were members. We have left, the grace periods are coming to an end, and the realities of leaving will slowly, but steadily, become clear.
We have no one to blame but ourselves. The rabid right wing press can chunter on about the hateful EUSSR all they like, but it's a self imposed mistake we have made.
WTO rules are coming after the grace periods end. I've not heard one brexiteer explain what those rules mean. It's just a wishy washy mishmash of stopping illegal immigrants without any recognition or understanding of what 3rd country status means, and we can't stop the boats coming anyway.
It is what it is, and it's a shitshow of bullshit, lies and deceit.