When Boris Johnson as PM agreed the Northern Ireland protocol as part of Brexit, many members of Northern Ireland’s unionist DUP hated it for a simple principled reason.
It kept Northern Ireland in the EU’s single market for goods and food, so when EU laws change relating to that market, Northern Ireland has to follow the new laws.
This has two negative consequences for NI unionists.
First, it separates NI in a constitutional sense from the rest of the UK, and therefore undermines the sovereign unity of the UK. Second, it makes NI a powerless rule-taker from Brussels, with no voice on important laws that affect NI.
The DUP told Johnson they hated the Protocol. He told them to relax because he was sure that one day soon he would be able to rip it up.
Now you will have read and heard a great deal about make-or-break talks between Johnson’s successor Sunak and the EU to fix the alleged flaws in the Protocol. And until today you probably expected a great breakthrough by close of play tomorrow - though that prospect is now highly remote.
But as and when said breakthrough happens, possibly later this week, this essence of the Protocol, what unionists see as the democratic deficit forced on the province, will not be eliminated.
And the reason is one that Johnson and all Brexit cheerleaders have known and accepted since they led the campaign to take the UK out of the EU and then negotiated the Brexit terms, namely that the absence of border checks on the island of Ireland - an absence vital to peace on the island - requires NI goods and food to comply with EU laws.
Just to be clear, this is a qualitatively different issue from the main set of problems supposedly being sorted by the current talks between Sunak and his EU interlocutors.
They are largely practical questions about how to eliminate checks on flows of goods and food from GB to NI, when those products are destined to remain in NI. Technology is delivering a solution.
Even the supposedly thorniest problem, how to remove or minimise the power and scope of the European Court of Justice in trade disputes relating to NI, is amenable to a technical solution, modelled on the precedent of the European Free Trade Association - though in practice I would expect the ECJ’s role to be significantly reduced rather than removed altogether.
But I cannot see any practical basis for absolving NI from the requirement to follow the rules of the EU’s internal market, or at least not without re-introducing a hard border between Northern Ireland and the Republic, and thereby breaching a fundamental principle of the Good Friday Agreement.
That said, it is highly likely Brussels will offer Stormont a voice when relevant single-market rules are being changed. But a voice is neither a vote or a veto. So the democratic deficit would remain.
So the big decision for the DUP is whether it can belatedly accept that Brussels, not Westminster, is the boss for important laws.
If it can’t, then it will not allow the Northern Ireland Executive and Assembly to be re-convened - and according to some unionists that would imperil the whole devolved settlement in NI (and by the way President Biden would not bother to visit Ulster on 10 April to celebrate the 25th anniversary of the Good Friday Agreement).
So for the DUP - and by implication for Johnson, Rees-Mogg and other Tory Brexiters - it is not just the fine print of what Sunak agrees that matters.
It is whether they accept finally and definitively that Brexit for Belfast can never be the same as for the rest of the UK, that the price of the Good Friday Agreement and peace is that NI can’t take back control.
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