When Geoffrey Cox was Theresa May’s Attorney General it was his refusal to go give his blessing to her Brexit deal that ensured her party would not vote for it. His reputation as a man with unbending principles meant many MPs simply took his word for it: if No10 said one thing and Cox said another they’d believe Cox. But now these Brexiteers have a conundrum, because in an article for The Times, Cox has just said he won’t vote for Boris Johnson’s Internal Market Bill.

Why not? Because it violates the terms of a treaty signed by this Prime Minister and ratified by this parliament. Here’s his argument..

“When the Queen’s minister gives his word, on her behalf, it should be axiomatic that he will keep it, even if the consequences are unpalatable. By doing so he pledges the faith, honour and credit of this nation and it diminishes the standing and reputation of Britain in the world if it should be seen to be otherwise. No British minister should solemnly undertake to observe treaty obligations with his fingers crossed behind his back. The Withdrawal Agreement and its attendant Northern Ireland Protocol represent treaty obligations of this country to which the government, in which I had the honour to serve as attorney-general, gave its solemn and binding word. It is, therefore, obliged to accept all the ordinary and foreseeable consequences of the implementation of that agreement.”

So the Bill is asking Parliament to go back on its word. It was Cox who advised Boris Johnson about the legality of the prorogation of parliament – he’s not one to avoid a fight. But draws the line at breaking his word.

“If the powers that the House of Commons is asked today to confer on the government by assenting to the UK Internal Market Bill are to be used to nullify those perfectly plain and foreseeable consequences, they would amount to nothing more or less than the unilateral abrogation of the treaty obligations to which we pledged our word less than 12 months ago, and which this parliament ratified in February. It is unconscionable that this country, justly famous for its regard for the rule of law around the world, should act in such a way.”

He makes the point that James Forsyth made recently – if the EU does play hardball and threaten to stop allowing food to be sent to Northern Ireland there are remedies for this inside the existing Treaty. You don’t have to break away from it.

“There are clear and lawful responses available to Her Majesty’s government, but both the spirit and the letter of the law require that these should be undertaken solely to accelerate progress in negotiations not as a means to force their abandonment… Therefore, if the government does not urgently and effectively dispel the impression that it intends to do so, I shall have no choice but to withhold my support for this Bill. I am a strong supporter of this government and of Brexit and I am deeply saddened to have to say this. We, the British government and parliament, have given our word. Our honour, our credibility, our self-respect and our future influence in the world all rest upon us keeping that word. Nothing less is worthy of Britain.”