The coming days are critical for NI's status within UK

The final shape, or proposed final shape, of Brexit is coming into view.

Two weeks ago this newspaper asked Downing Street about the possibility of ruling out a regulatory border in the Irish Sea. We did so because the government’s emphatic refusal to countenance an internal UK border had increasingly been accompanied by the words “customs”.

But customs is only half of the equation. Regulations are the other half. The Irish government knows this only too well. It has ruled out either a regulatory or customs land border in Ireland.

It is important to emphasise this. Dublin has not merely ruled out checks, it has (in effect) ruled out divergence on the island. This is its interpretation of the disastrous backstop of last December.

As the pro Brexit commentator Andrew Lilico has written on these pages, the UK should have walked out of talks with the EU once the latter’s uncompromising interpretation of the backstop fudge became clear. Instead, the UK has tried to reconcile its interpretation with that of the EU’s.

There is talk of a UK-wide customs union arrangement with the EU and Northern Ireland staying in regulatory alignment.

There is already a small amount of regulatory checks at ports relating to things such as animal standards. This could perhaps be expanded very slightly.

Anything more than that and the DUP will probably have to end its current relationship with the government. It has no other card to play. Otherwise it is (in effect) acceding to the principle that Northern Ireland must at all times be in full customs and regulatory alignment with the EU, regardless of how much the rest of the UK might one day diverge from EU standards. This would be entirely unacceptable and a body blow to NI’s status within the UK.