o the patron saint of modern Conservatives, the rule of law was always fundamental to economic prosperity. It was also always distinctively British. In her memoirs, Margaret Thatcher identified the rule of law as the foundational underpinning of commercial confidence in any society. And in a 1982 interview she said that Britain gave the very idea of the rule of law to Europe. As she put it: “The law came from us.” Thatcher also shared the view of her favourite lawyer, Lord Denning, that the law should uphold the keeping of promises. She extended this to upholding the obligations of international treaties too. In 1975, she told the Tory women’s conference that: “In the same way that government and individuals should be bound by law so countries should be bound by treaties.” She added: “Britain does not renounce treaties. Indeed, to do so would damage our own integrity as well as international relations.” Most Conservative MPs today still venerate Thatcher. But if that veneration means anything, there is no way those MPs should vote for the United Kingdom internal market bill that Boris Johnson published on Wednesday. The bill does not merely assert the right to override aspects of the EU withdrawal agreement relating to Northern Ireland. It also establishes, as a potential precedent, the UK’s claim to a right of unilateral derogation from international treaties. No wonder the former Labour attorney general Lord Goldsmith is spearheading an all-party campaign to pay much more parliamentary attention to treaties. For a British government under the influence of Dominic Cummings to plan to break its promises on the world stage comes as no surprise. The No 10 adviser’s defiance of his own government’s Covid-19 lockdown measures in March destroyed much of the public’s trust in the handling of the pandemic. Cummings’ refusal to apologise confirmed that his default setting was that rules and laws, like taxes, were for the little people, not for masters of the universe like him. The new bill transplants those claims to be above the law on to the international stage. Even so, it is a jaw-dropping move from a country that normally counts itself among the most law-abiding on the planet. It says, in fact and in effect, that an independent nation state, providing that it is called the UK, can behave in whatever way it wants in its relations with other nations. Perfidious Albion, indeed. If the lord chancellor, Robert Buckland, and the attorney general, Suella Braverman, approved this bill they should resign. It is nevertheless important to stop and think about the politics of all this. It is true that, in the Cummings view of the world, the words uttered in the Commons by the Northern Ireland secretary, Brandon Lewis, this week – “Yes, this does break international law” – are absolutely fine. Cummings and Johnson, after all, did not get where they are today by respecting either conventions or foreigners. But there is also a large measure of bluff going on too. Most immediately, No 10 believes that shifting the political conversation from Covid to Brexit works to its advantage. Public opinion on Covid-19 mainly follows party lines. So as the polls shift against the Conservatives, and the crisis enters a new and difficult phase, with cases rising, it suits Cummings and Johnson to move to Brexit, where opinion is far more entrenched on both sides. That is why Keir Starmer very obviously passed up the opportunity to quiz Johnson on the law-breaking new Brexit bill on Wednesday at prime minister’s questions. Nothing would have delighted Johnson more than to draw Starmer, who regularly defeats him at PMQs, off Covid and on to Brexit territory. But the law-breaking bill rolls the dice in other ways. The clock is ticking in the EU talks. If Johnson wants a deal, he will feel he has to present it to leavers as a triumph snatched from the EU against the odds. He cannot simply go into the talks and reach agreement. If he did, the hardest Brexiters – who do not want a deal – would say he had bowed the knee to the foreigners. Instead, Johnson has to create a smokescreen crisis that annoys the European side enough to allow him to emerge from the confusion with a supposedly hard-won deal. The big unknown remains whether Johnson really desires an agreement. Here is one reason why he may. He really does not want the UK to break up. The dangers of that possibility have finally been borne in on him this summer, not before time. But a no-deal exit would turbo-charge Nicola Sturgeon’s campaign to take Scotland out of the UK. An EU deal, on the other hand, would at least mitigate that outcome. It would offer more certainty for the Scottish economy. It would not stop the independence campaign, but it would not put booster rockets under it in the way a no-deal exit would. It is this, more than any other factor, that suggests the law-breaking parts of the new bill may not reach the statute book in the end. However, Johnson and Cummings may prefer to fight the mother of all battles over Brexit because, in the end, that is the reason why this government exists. If so, the many remaining Thatcherites on the Conservative benches should reflect on what that means. For Thatcherism has now been conclusively hijacked by Johnson and Cummings. They will never get it back again. Thatcher would have thought she knew the consequences of Britain defying international law. In that same 1975 speech she said: “If governments do not respect the law it is little wonder that some individuals come to think they can bypass it too.” Welcome to Johnson’s and Cummings’ world, in which the government actively seeks disorder and law-breaking. This is indeed a very different kind of Tory party from any of its predecessors. • Martin Kettle is a Guardian columnist