Boris Johnson’s first speech in office extolled the virtues of “habeas corpus and the rule of law”. But three years later, the prime minister stands accused of trying to break international law twice in a week – on the Northern Ireland protocol and steel tariffs.

The latter led to the resignation of his ethics adviser, Lord Geidt.

It was also the week in which Johnson alarmed many in his own party, as well as in the legal profession, by suggesting that the UK could withdraw from the European convention on human rights. This was in response to a last-minute court order that halted his plans to deport people seeking asylum to Rwanda.

Johnson’s critics say his approach of changing or breaking the rules when they do not suit him has been his playbook throughout his political career, whether by changing the standards system, overhauling judicial review or proroguing parliament to avoid scrutiny. Nowhere is this more evident than his police fine for breaking the Covid lockdown laws that he had brought into force, which has earned him the dubious distinction of being the first sitting UK prime minister to have personally broken the law.

“The government confirmed it will change the law so it can ignore injunctions from the European court of justice retraining government action. The independent ethics adviser may not be replaced. The judicial review act now allows courts to ignore past breaches of law by the government on JR. The trend is clear,” observed Charlie Falconer, the Labour peer and former justice secretary.

The government’s “cavalier” approach toward the law under Johnson appears to be new, said Jill Rutter, a senior fellow at the Institute for Government and the UK in a Changing Europe.

Politicians railing against court judgments – particularly European ones – for the benefit of the rightwing press has long been a recurrent theme, she said. But she added that there was a sense among experts on government that Johnson’s administration has taken this further.

“We always says we’re interested in upholding an international rules-based order, but I think the bit that is new is the unembarrassed, flagrant proposal around the Northern Ireland protocol and making commitments that we then denounce relatively soon thereafter,” Rutter said.

Rutter said Johnson appeared to subscribe to “the divine right of the popular will, seeing any restraint on getting its way as illegitimate”.

Despite his fall in the polls, Johnson appears still to believe himself in tune with the public. “If you think you’re in a Spock-like mind-meld with the British people, then everything else is illegitimate, and I think that’s a sort of Johnsonian post-Brexit mindset,” she said. “They seem more unembarrassed by untrammelled executive power than any other government I’ve seen.”

Johnson’s first clashes with the law came early in his premiership, when he attempted to prorogue parliament for five weeks at the height of the Brexit crisis – a move that was ruled unlawful by the supreme court.

With his leadership on the rocks, there is a sense that Johnson may again be ramping up populist tensions with the law – especially on matters relating to Europe – as part of a fresh “people versus the establishment” narrative.

Sir Roger Gale, a Conservative MP and one of the prime minister’s biggest critics from his own benches, said the breach of international law in relation to the Northern Ireland protocol was particularly concerning.

“We don’t break international law. If we do, we have no right to criticise other countries when they break international law, and that of course would include the Russian Federation as well as anyone else,” he said. “We should be sitting down and talking to people in a civilised manner … We cannot go on scoring political points over Europe. It’s like the PM is a one-trick pony. All he’s got is Brexit and he wants to rub it in on every occasion because that’s his USP. We need to move on.”

He said the approach to the European court of human rights and the Rwanda decision was also a “dog-whistle, kneejerk response” and an example of “more Europe-bashing” when the court is associated with the Council of Europe, not the European Union.

Within the legal community, there have been wider concerns about the Conservative government’s approach to the law, including the failure of the lord chancellor and attorney general to stand up for judges in the face of pressure and abuse.

A highly critical report from the all-party parliamentary group on democracy and the constitution found earlier this month that ministers had acted improperly by questioning the legitimacy of judges and threatening to reform the judiciary. They argued that this had created an impression that recent supreme court decisions favourable to the government may have been a response to political pressure.

Ellie Cumbo, head of public law at the Law Society, said the job of the lord chancellor, currently Dominic Raab, the deputy prime minister, was a “constitutional grey area” when it came to how far he should go in sticking up for the judiciary.

She said every time inflammatory language around judges, immigration decisions or judicial review were challenged, the government appeared to take an approach of “ramping up those accusations and misleading rhetoric” rather than dampening it down.

“It’s not clear where it’s going to end,” she said.