LONDON — There's a new Brexit deal in the works: Britain will close its eyes if Europe bites its tongue.

In a bid to get Theresa May's deal over the line — and stop a Brexit delay of 21 months or longer — the U.K. government has turned to an obscure clause in an obscure international treaty to prove to hard-line Euroskeptics that there is a way out of the Irish backstop.

With May's Brexit deal likely to be voted on in the House of Commons this week for a third time, ahead of the prime minister traveling to Brussels on Thursday to seek an extension of Article 50 irrespective of whether or not her deal passes, London is looking for creative — some say dubious — ways to bring opponents on board.

That's where Article 62 of the Vienna Convention — a treaty that lays down the rules about international treaties, or legal agreements between countries — comes in.

Under one option set out by the Brexit Secretary Steve Barclay, the U.K. could make a statement saying that if there are "unforeseen circumstances" arising from the implementation of the backstop, the U.K. would have the right to walk away.

Barclay confirmed the U.K. is looking at this scenario in a parliamentary answer to Conservative MP Jacob Rees-Mogg last week.

Barclay spelled out one possible “unforeseen” circumstance in his answer to Rees-Mogg. He said if the U.K. deemed that the backstop was “no longer protecting the 1998 [Good Friday] agreement in all its dimensions,” that could be enough for the U.K. to pull out of it.

In other words, if the backstop, which is there to protect the open border in Ireland — a central part of the peace process — is later seen to be actively undermining the peace process, the U.K. could seek to declare the arrangement null and void.

The problem for the U.K. government, according to EU officials aware of the proposal, is that "unforeseen circumstances" are hardly that if they are known about in advance.

One international law expert, who did not want to be named, said the Vienna Convention argument is “weak.”

One senior government official from an EU27 member country said the EU would “not be surprised to see a truly unilateral declaration of this or another sort tried out” over the coming days. “The question for us would be how far to bite our tongues,” the official said.

If the EU does bite its collective tongue, the U.K. government hopes Brexiteers will close their eyes to what many experts and EU officials believe is the dubious legal basis of the Vienna Convention option in a bid to get the deal done.

If the EU and the Brexiteers both play their part, the argument goes, the Brexit deal might still have a chance of passing.

Changes in the small print

The Withdrawal Agreement drawn up by the U.K. and EU states that the backstop is necessary to protect key elements of the Good Friday peace agreement.

One section of the backstop text acknowledges that it is needed "so as to maintain the necessary conditions for continued North-South cooperation … in accordance with the 1998 Agreement.”

However, in the joint "instrument” subsequently agreed by both sides — which provides interpretation of the Withdrawal Agreement — the relationship between the backstop and the Good Friday Agreement appears to have changed.

Instead of being “necessary,” the joint instrument says the new structure of governance for Northern Ireland contained in the backstop “does not affect or supersede the provisions of the 1998 Agreement in any way.”

It adds that the backstop does not alter “in any way” those areas where Belfast and Dublin agreed to work together under the terms of the Good Friday Agreement. These areas will continue to be “matters for the Northern Ireland Executive and Government of Ireland to determine,” the joint instrument states.

Unionists briefed on the matter say this section is key because it suggests the U.K. government is concerned the backstop, far from being “necessary” to protect the Good Friday Agreement, may, over time, serve to undermine some of its core provisions. Nationalists in Northern Ireland — and EU officials — fiercely dispute this.

Nevertheless, by inserting the clause into the joint instrument, the U.K. has set up an extra test for the backstop that ministers believe could justify withdrawal should the backstop ever risk becoming permanent.

Addressing Rees-Mogg on Tuesday, the Brexit secretary said the issue is whether there might be “exceptional circumstances that might change the basis on which the U.K. might enter into an agreement.”

He explained: “If the United Kingdom took the reasonable view, on clear evidence, that the objectives of the protocol [backstop] were no longer being proportionately served by its provisions — because, for example, it was no longer protecting the 1998 agreement in all its dimensions — the U.K. would first, obviously, attempt to resolve the issue in the Joint Committee [to be set up as part of Withdrawal Agreement] and within the negotiations.

“However … it could respectfully be argued, if the facts clearly warranted it, that there had been an unforeseen and fundamental change of circumstances affecting the essential basis of the treaty on which the United Kingdom’s consent had been given.”

In this instance, Barclay said, “Article 62 of the Vienna Convention on the law of treaties … permits the termination of a treaty in such circumstances.”

He added: “It would, in the government’s view, be clear in those exceptional circumstances that international law provides the United Kingdom with a right to terminate the Withdrawal Agreement.”

A senior official from an EU27 member state dismissed the basis of the argument, saying it is perfectly possible to foresee that it would not be possible to find an agreed solution to the Irish border.

The official added that the regulation of trade between Northern Ireland and the Republic of Ireland “is not and never has been a competence of the GFA [Good Friday Agreement] institutions.”

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