Dominic Grieve should be applauded for putting commitment to the rule of law ahead of his party’s short-term political advantage.

If the prime minister wants to see you in his Commons room on reshuffle day, you know it is going to be bad news. Until the call came three weeks ago, Dominic Grieve had not been expecting to lose his job as attorney general just 10 months short of a full five-year term.

David Cameron offered him no explanation, Grieve tells me. But Downing Street dispelled any doubt in a briefing to the BBC’s political editor. The Conservatives were drafting a manifesto commitment on human rights and Grieve had argued against it in forthright terms.

For reasons that strike me as both insulting and shortsighted, Grieve was not shown a copy of the policy paper produced for his party last year. But he knows what it says.

‘The proposal that seems to have been floating about is that a Conservative government should enact primary legislation to state that, while Britain would still adhere to the European convention, no judgment of the European Court of Human Rights could be implemented without parliament having approved its implementation in some way.’

That sounds as if Britain is getting tough with Strasbourg. But any lawyer can see it would not work.

‘The convention is an international treaty,’ Grieve explains patiently. ‘It binds the United Kingdom by virtue of international law and the UK is under an obligation to give effect to decisions of the court. If the UK doesn’t like the decisions of the court or feels that the convention is not operating properly, it has the right to withdraw from the convention.

‘But it’s cherry-picking – and also a somewhat anarchic act – for a government to say: we are signatories but, by our own motion, we have decided to implement only those judgments that our parliament tells us we can.’

The problem, simply stated, is that national legislation cannot override a country’s international obligations. ‘Putin used the duma, in Moscow, to legitimise Russia’s seizure of Crimea,’ Grieve reminds me. ‘It does not make Russia’s seizure of Crimea lawful under international law.’

But Russia has, to some extent, got away with it. Wouldn’t a future Conservative government? ‘If the UK wishes to do this, it can,’ Grieve says. ‘The consequences seem to me to be political and reputational.’ He means that Britain would no longer be trusted to keep its word.

We might eventually be kicked out of the Council of Europe, which runs the human rights court. Grieve believes the EU Court of Justice in Luxembourg would then expand its role, requiring the UK to comply with human rights judgments. ‘And as it has been the centrepiece of government policy to try to restrict the remit of the Court of Justice to EU-related matters, that could have very undesirable consequences for us.’

There would also be practical problems for Grieve’s successor, Jeremy Wright, if a Conservative government tried to change the law. The attorney general would have to advise civil servants they could not even draft legislation that would be contrary to the ministerial code, which currently requires compliance with the UK’s international legal obligations.

What the Conservatives are now contemplating is something the UK has never done, despite signing more than 13,000 treaties since 1815. ‘It’s little short of revolutionary in terms of our constitutional arrangements in this country,’ the former attorney general continues. ‘It’s never been suggested before that the United Kingdom honours its international legal obligations only if parliament approves each individual act. And yet that is what is being contemplated here.’

As Grieve returns to the back benches for the first time since 1999, is he not in danger of becoming a lone voice? Surely voters will be attracted to a policy of giving the last word on human rights to parliament rather than foreign judges?

‘It does have certain superficial attractions but I think the electorate are quite clever at detecting what is serious in terms of change and what may just be window-dressing,’ he replies. If the policy makes it into the Conservatives’ manifesto, he will tell voters he cannot support it.

Grieve’s deputy, Oliver Heald, was also sacked last month. After serving as solicitor general for less than two years – plus two years as a junior social security minister under John Major and five years longer than Grieve as an MP – Heald was given the knighthood that used to be offered to all law officers on appointment. There was no such honour for Grieve.

Was this because he was not prepared to keep quiet? Taking my cynical question in his stride, Grieve won’t be drawn. ‘It’s a matter for the prime minister,’ is all he will say. But who needs a knighthood when you have something much more valuable: universal respect for putting commitment to the rule of law ahead of your party’s short-term political advantage.