Can Boris Johnson’s new plan to tear up the Northern Ireland protocol work?

The UK and the EU decided it was unseemly to fight over the Northern Ireland protocol when a real war erupted in Ukraine, but the ceasefire was never going to last.

Sure enough, battle is about to be waged anew, when Boris Johnson unveils his new cunning plan to torpedo the Brexit deal he negotiated and hailed as “fantastic” – before disowning it.

This time, the strategy is not simply to trigger the fabled Article 16, the threat to suspend offending parts of the protocol made, tediously, so many times last year, but never carried out.

The prime minister pulled back because of fears of a damaging trade war with Brussels, when the economy was only just emerging from its Covid deep freeze – but what is his new plan and is it any more viable?

The details are sketchy, but a bill is expected in next month’s Queen’s Speech to give the UK powers to override the need for trade checks on goods sent across the Irish Sea from Great Britain.

Ministers argue the red tape – to ensure goods meet EU regulations – is unnecessary if they are not being sold on to Ireland, despite signing up to those rules in 2019.

Some “red meat” will also be needed to persuade the Democratic Unionist Party to restore power-sharing if, as expected, Sinn Fein triumphs in crucial Stormont elections on 5 May.

Mr Johnson and Liz Truss, the foreign secretary, are said to have signed off the idea in principle, but it has not yet been discussed by the cabinet, ahead of the state opening on 10 May.

Now, it seems the government can switch off parts of the protocol without facing action in the UK courts – it’s Article 7a of the withdrawal agreement, apparently – but if that sounds too good to be true, well, of course it is.

It’s time to introduce the concept of “pacta sunt servanda”, which – if like me, you were not taught much Latin at your comprehensive school – means “agreements must be kept”.

It is said to be the oldest principle of international law, the basis for ensuring treaties are binding and enforceable, and the reminder that there are limits to “taking back control”, the Brexit mantra.

Of course, Mr Johnson can change UK law in (almost) any way it likes – but that does not allow him to rewrite an international agreement unilaterally, if his signature is on it.

Whether it’s Article 16 or something else, the EU will retaliate, possibly even moving to rip up the Brexit trade deal entirely, when unity over Ukraine is still needed so badly.

And that would happen amid a devastating cost of living crisis, when the government is too scared to impose long-promised checks on imports from the EU because of the economic pain that would bring.

The great irony is that a prime minister who has “apologised unreservedly” for breaking domestic law is now contemplating breaking international law as well.

Maybe it is his attempt to finally give teeth to his phrase “Global Britain” – but, joking aside, it is unlikely to end any more happily.