Alas, Vienna convention isn’t the magic bullet to the deal’s key problem

After the Attorney General’s legal advice doomed Theresa May to another Commons defeat this week, the search was back on in earnest yesterday to find reasons for Brexiteers to vote for her deal when it comes back for a third time.

Geoffrey Cox’s warning – the “legal risk remains unchanged” that the UK could be trapped indefinitely in the Irish backstop – left Brexiteers with no choice but to vote against the deal.

However, in that lethal final paragraph, Mr Cox left a tiny caveat, which was that this judgment would pertain “at least while the fundamental circumstances remained the same”. This was a reference to Article 62 of the Vienna Convention on the Law of Treaties (VCLT) that allows treaties to be terminated in the event of a “fundamental change of circumstances”.

The possibility that this could be the “get out” card that Brexiteers needed was then given wings by Stephen Barclay, the Brexit Secretary, after he was questioned in the Commons about the potential of Article 62, from Jacob Rees-mogg, the dean of Tory Eurosceptics.

Mr Barclay said the UK would indeed have the ability to terminate the Withdrawal Agreement “if the facts clearly warranted that there had been an unforeseen and fundamental change of circumstances”.

Could Article 62, then, be the magic bullet that could allow Brexiteers to say that the UK did, after all, have the right in international law to quit the backstop?

Mr Cox has now elaborated on this caveat and clarified that advice, which could provide the ladder down which Tory Brexiteers could climb to support Mrs May’s deal, if only because it was better than a long delay – or no Brexit at all.

Alas, even before the Eurosceptic “Star Chamber” of legal experts had delivered its verdict on Mr Cox’s new advice, leading international lawyers queued up to point out that under Article 62, the “fundamental change of circumstances” needed to justify terminating a treaty had to be something that was “not foreseen by the parties”.

Given the acres of verbiage that have been expanded on the risks of being “trapped” in the Irish backstop, this would be clearly be impossible to argue. There really is nothing new left in Brexit, so it wasn’t long before it was pointed out that the impartial House of Commons library had addressed the utility of Article 62 in a report last December and had concluded that it would be “extremely difficult” to use it.

The final nail in the coffin came when Martin Howe QC, a member of the Brexiteer “Star Chamber”, pointed out that in one case even “the fall of the Soviet Union” had not been deemed sufficient grounds. The Article 62 dog, it seems, does not hunt.

At the same time, there are renewed efforts to try to woo the Democratic Unionist Party with fresh guarantees that Northern Ireland will not be left in a world apart if the backstop does kick in. Arlene Foster, the DUP leader, said that she wanted measures to ensure “the constitutional integrity of the UK is the same and we have a strong say in the future” – which is what is being called a “Stormont Lock”.

In essence, the DUP wants the Government to honour the pledge set out in Paragraph 50 of the Joint Report of 2017 that the backstop will not allow “new regulatory barriers [to] develop between Northern Ireland and the rest of the United Kingdom” and retain Northern Ireland’s “unfettered access” to the UK’S own internal market.

The UK Government pledged in January in a Cabinet paper that there will be “no divergence in practice” between Great Britain and Northern Ireland if the backstop takes effect, but the DUP dismissed it out of hand at the time as “cosmetic and meaningless”.

The difficulty is that additional checks in the Irish Sea are inherent in the backstop and legal guarantees that Great Britain would remain in lockstep could see Northern Ireland become the tail that wags the dog – and deny Brexiteers the freedom they seek to diverge from Europe.

The question now is whether some form of reboot or reinforcement of the January Cabinet Paper can bring the 10 DUP members on board, and with them (Downing Street hopes) the bulk of the rebel European Research Group.

These are difficult asks up to and including – per one DUP source – amending the Unilateral Declaration agreed with the EU in Strasbourg last week to reflect any new guarantees.

Given the EU’S blanket refusal to reopen negotiations, that looks like a long shot indeed.