The Prime Minister and European Commission President Jean-Claude Juncker on Thursday announced the two sides have come to an agreement on a “great new deal” for Brexit, ahead of a crucial EU summit in Brussels.
Mr Johnson tweeted that the new Withdrawal Agreement “takes back control” and removes the “anti-democratic” Irish backstop, although the Tories’ Northern Irish allies in the DUP have indicated they cannot support the deal.
Good Law Project founder Jolyon Maugham QC, who says he will submit the emergency legal challenge to Scotland’s highest civil court, has warned the Withdrawal Agreement is unlawful - under legislation put forward by the Conservatives’ right-wing group of MPs known as the European Research Group (ERG).
EU chief negotiator Michel Barnier has revealed the deal means Northern Ireland will remain in the UK’s customs territory but that the island of Ireland will be aligned to some EU rules, meaning goods must be checked on entry to the island rather than border checks between Northern Ireland and the Republic.
Mr Barnier said: “We are fully committed to protecting peace, to protect stability on the island of Ireland,” adding that a hard border would be avoided while protecting the integrity of the single market.
Explaining his legal objections to the agreement, due to be debated in a special Westminster sitting on Saturday, Mr Maugham said it contravenes legislation stating it is “unlawful for Her Majesty’s Government to enter into arrangements under which Northern Ireland forms part of a separate customs territory to Great Britain”.
Under the current law, Section 55 of the Taxation (Cross-border Trade) Act 2018 prevents Northern Ireland from having different customs rules than the rest of the UK, purportedly to “uphold the constitutional integrity of the United Kingdom and safeguard the Union for the future”, according to a Government briefing on the Bill.
After details emerged of the Brexit deal, Mr Maugham - whose legal team took action to try and ensure the Prime Minister obeys by the Benn Act - said: “I intend to launch an immediate petition for an injunction in the Court of Session preventing the Government from placing the Withdrawal Agreement before Parliament for approval.”
He has said the petition is expected to be heard on Friday, and added: “We do not understand how the Government might have come to negotiate a Withdrawal Agreement in terms that breach amendments tabled by its own European Research Group.
“Unless and until Section 55 is repealed by the UK Parliament, it is simply not open, as a matter of law, for the United Kingdom to enter into such an agreement.
“If the proposed Withdrawal Agreement is unlawful, the Government will be obliged to request an extension as mandated by the Benn Act and in accordance with undertakings given to the Court of Session in Vince, Maugham, Cherry v Boris Johnson.”
Writing on Twitter, Mr Maugham called on the Government not to present “an unlawful Withdrawal Agreement to Parliament” and instead request an extension under the terms of the Benn Act to allow MPs to consider - and make lawful - the deal.
Mr Maugham added: “Here we are, after three and a half years, and it looks as though Parliament will be asked to approve on Sat a 500+ page document which it has not seen (indeed which does not yet exist) with epochal consequences for Great Britain, Northern Ireland and the EU and in short time.
“If the Government wants to seek Parliament’s consent to repeal section 55, it can and should seek that consent.
“But it must not negotiate unlawful trade deals and then present them to Parliament as a fait accompli.”
Mr Maugham also argued the Government will prevent Parliament from having any say on future trade negotiations, “including those affecting the NHS”.
He added: “That should cause deep alarm to all of us.”