Claims that the UK government has discovered a legal justification for tearing up large parts of Brexit arrangements in Northern Ireland have been greeted with scorn by expert lawyers. The attorney general, Suella Braverman, has reportedly approved overriding the Northern Ireland protocol on the grounds that it is being unfairly enforced by the EU. Her submission, understood to be based on external advice, claims the EU’s “disproportionate and unreasonable” implementation is undermining the Good Friday agreement (GFA), according to the Times. But George Peretz QC, a barrister who specialises in EU law, told the Guardian: “I can’t see how any lawyer could possibly advise the government that they’ve got a slam-dunk case. What I’ve seen so far doesn’t give them sustainable legal cover.” Sir Jonathan Jones, who resigned as head of the government’s legal department in 2020 when ministers last threatened to ditch parts of the protocol, told BBC Radio 4’s PM programme: “The government knew about the Good Friday agreement when it entered into this protocol, and the protocol is said to be a way of protecting the interests of the Good Friday agreement. So the idea that now becomes a basis for walking away from the protocol I think is very problematic.” On Thursday the foreign secretary, Liz Truss, reiterated UK plans to scrap parts of the protocol, telling the EU’s Brexit negotiator it was a matter of “internal peace and security”. According to the Times, Braverman’s advice says the GFA has “primordial significance” over the protocol and its current implementation is creating “societal unrest”. Peretz said: “‘Primordial significance’ is not a legal term that I’ve ever come across.” Catherine Barnard, a professor in EU law at Trinity College, Cambridge, agreed. She said: “There is no hierarchy of treaties in law. The GFA may be a political priority, but it has no primacy in law.” She said the UK could come up with a legal argument for invoking article 16, which allows for suspending some obligations under the protocol, if specific difficulties could be proved. But this was “very limited” in scope and time, and subject to review. She said the legal requirement for ditching the protocol was “an extremely high bar”. Peretz reckoned the government would struggle to justify invoking article 16 based on economic problems, because these were known about in advance. “It was pretty obvious to both parties that putting a border down the Irish Sea was going to divert trade, so that would be a bizarre argument,” he said. He added that growing sectarian tensions, reportedly cited by Braverman, would not be enough to overturn an international treaty. “In international law, social unrest is not a basis for denouncing a treaty which you’ve signed,” Peretz said. Braverman’s reported claim about the primacy of the GFA over the protocol also runs counter to the text of the agreement, Peretz said. “Article 1.3 says the protocol is not only consistent with the GFA but necessary to it,” he said. He pointed out that this principle had been upheld in the court of appeal. “The government itself has argued strenuously in court that the protocol is entirely consistent with the GFA, so I don’t see how this can possibly get off the ground.” Barnard called for Braverman’s advice to be made public. Peretz said the government may be reluctant to publish. He said: “When I was a government lawyer 30 years ago, it was drummed into me that you never ever published the attorney general’s advice. The advice may be guarded and nuanced, and say that the arguments against are quite strong. To publish something like that is not that impressive.” Some lawyers have backed the government’s plans for a bill to override the protocol. They include Martin Howe, the chair of the pro-Brexit group Lawyers for Britain. In a Telegraph article last month, he wrote: “The EU must be brought to recognise that no sovereign and independent state can long tolerate a part of its territory being subject to foreign courts and laws. The EU would understand that once the bill became law they would lose the power to continue to impose the protocol.” Peretz said this was a minority view among lawyers. He said: “If the advice is all about the conditions for exercising article 16, this is something the government might arguably be able to run. As to whether there’s an argument for simply ditching parts of the treaty on the basis that the text isn’t binding on the UK any more, that’s much more difficult. And I think there’s general agreement about that.” He added: “I have no idea the extent to which the government has hawked around the bar until it found a lawyer who is prepared to say what it wants. But that’s possible.”