Britain has a decision to make: the rule of Boris Johnson – or the rule of law?

Don’t succumb to Johnson derangement syndrome, they tell us. Stay calm. Keep a sense of proportion. Don’t get carried away. As a matter of self-care, that might be good advice for those at risk of bursting a blood vessel in their rage at this government and its leader. But learning to shrug off Boris Johnson’s conduct carries risks of its own. It can mean missing, or underreacting to, acts that merit furious opposition – such as when, before our very eyes, the prime minister destroys the principle that sits at the very foundation of a free society, a principle first codified in this country eight centuries ago and without which a life free of fear is impossible. I’m talking about the rule of law.

It’s so basic, we take it for granted. It’s the notion, spelt out in Magna Carta in 1215, that even those in power do not enjoy unlimited or unfettered authority, but are constrained by rules; that even the sovereign – the state – is subject to the law of the land. Only then can citizens feel relatively safe from the threat of arbitrary power, safe from a king – or prime minister – doing whatever the hell he likes.

After 1945, having witnessed the murderous horrors of totalitarianism and seen where unchecked state power could lead, Britain and the US moved to expand the Magna Carta principle. From now on, states would be subject to the constraint not only of their own domestic law, but international law too. The world after Hitler would be a rules-based order.

But look at things now. “We’re fucking breaking international law like it’s one of our five a day,” one government official tells Politico. The frequency is indeed striking. On Monday the foreign secretary, Liz Truss, presented a bill to “fix” the Northern Ireland protocol, “disapplying” – ignoring – those post-Brexit trade rules the government now finds inconvenient.

Put aside the crude politics of it: ramping up yet another battle with Brussels because that was the playbook Johnson won with, and he knows no other. Put aside the fact that most citizens in Northern Ireland not only voted against Brexit but voted for parties that support the protocol and don’t want to see it scrapped. Put aside the stinking hypocrisy of a government complaining about the terms of an agreement it itself negotiated, praised and pushed through parliament just two years ago.

Focus instead on what is actually happening here. The UK government is breaking a binding international legal agreement, and admitting as much in the text of its bill, which invokes the “doctrine of necessity” in seeking to justify its violation of its obligations (a doctrine that doesn’t, in fact, apply when the “necessity” arises only because of policy decisions the government itself took). No wonder there is alarm in Washington as well as in EU capitals: a nation that 80 years ago was leading the way in establishing a rules-based order is now apparently bent on destroying it. The New Yorker calls Britain a “rogue nation”.

That was the clear message that came the day after the Northern Ireland “fix”, when in an 11th-hour ruling the European court of human rights blocked the transfer of a handful of asylum seekers from Britain to Rwanda. Again, ignore the gross culture war motivation behind this policy, the naked desire to rally the 2016 anti-immigration base, to enjoy again the thrill of bashing do-gooding lawyers and “European judges” (even though the ECHR has nothing to do with the EU). Put aside the cruelty of dumping desperate people in a faraway land, the callousness of trying to outsource Britain’s moral duty – because providing safe harbour to refugees is a moral duty – to an authoritarian state.

Focus instead on the fact that this move was found to be a violation of a convention on human rights drafted in part by David Maxwell Fyfe, a Conservative politician, member of Winston Churchill’s cabinet and onetime prosecutor of Nazi war criminals at Nuremberg. And note Johnson’s response when asked if Britain should withdraw from the ECHR it had helped create, given the obstacles the convention was placing in the way of the Rwanda policy: “Will it be necessary to change some laws to help us as we go along? It may very well be.”

The next day, Wednesday, Christopher Geidt resigned as the PM’s ethics adviser, apparently, if not wholly credibly, over a decision on trade policy: tellingly, the move he was asked to approve would have clashed with Britain’s obligations under WTO rules. The pattern is plain enough. Without much publicity, the government has, for example, entirely ignored rulings in 2019 and 2021 by the international court of justice and the international tribunal for the law of the sea outlawing Britain’s continued occupation of the Chagos islands in the Indian Ocean. As Philippe Sands QC, who has acted in the case, told me: “Britain’s reputation is uniquely built on the rule of law – and this government is trashing it.”

Of course, the international violations mirror the domestic ones. Whatever the precise nature of the last straw, Geidt’s back was broken by the serial rule-breaking of the man he served. Every single minute that he has been prime minister, Johnson has been under investigation, culminating in the fine he received for breaking the law by partying during lockdown – and his refusal to resign once he had. But none of that should have come as a surprise. Johnson demonstrated his contempt for the law within weeks of taking office by proroguing parliament, seeking to bypass and silence the nation’s elected representatives. The supreme court thwarted him, but his attitude was clear. “We used to be a country where the rule of law really mattered,” says the chair of the Commons standards committee, Chris Bryant. “All of that is thrown away.”

Gideon Rachman’s new book, The Age of the Strongman, includes Johnson alongside the likes of Donald Trump, Recep Tayyip Erdoğan and Viktor Orbán – and this, despite the obvious differences, is one of the chief reasons why. What these men have in common is disdain for any constraint on their own power. If the law enables them to have their way, then it is legitimate. If it does not, it can be broken or ignored. Those who insist on it – lawyers and judges, for example – are demonised as politically motivated partisans, meddling, out-of-touch elitists, “enemies of the people”.

Yet the rule of law is anything but the preserve of the elite. It is the last, most precious protection of the weak against the whims of the strong. It is what stands between us and tyranny. Our prime minister poses a grave threat to it – and it’s not deranged to say so.

• Jonathan Freedland is a Guardian columnist