Tuesday, 19 January 2021 was the last full day of Donald Trump’s administration. Among its final acts was to declare the Chinese government’s treatment of Uighurs in Xinjiang province to be an act of genocide. What to do about that is President Biden’s problem.

Whilst the US Secretary of State, Mike Pompeo, can pronounce genocide where he suspects it, his British equivalent plays it by the book. Last week Dominic Raab announced a raft of measures designed to reduce the possibility of goods linked to Uighur forced labour entering British supply chains. But on whether the treatment of those Uighurs amounts to genocide, Raab honours the British tradition of leaving it to the institutions of the UN to determine what meets its own Convention’s genocide threshold.

The jurisdiction of the International Criminal Court does not run to non-members like China and given Beijing’s power – direct and indirect – in the UN, there is no likelihood of China being weighed in the balance and found genocidal. Indeed, obedience to international law has helped ensure that not since Nuremberg has the British government declared a genocide to be in progress.

Whilst Pompeo was finding the Chinese state guilty, the House of Commons was debating a range of Lords’ amendments to the Trade Bill, the most contentious of which was to give the High Court of England and Wales the power to issue a preliminary determination that genocide had taken place and for this judgement to automatically void any British free trade agreement with the guilty country.

The amendment was in the name of the crossbench peer, Lord Alton, the breadth of its appeal evident in its principal backers, Lord Adonis and Lord Forsyth of Drumlean (the former Tory Scottish secretary, Michael Forsyth). In the Commons, it also brought together former Remainers and Brexiteers. Iain Duncan Smith spoke for several Brexiteers (among the 34 Tories voting for the amendment were Bernard Jenkin, Mark Francois, Andrew Rosindell and Philip Hollobone) when he said that the country had left the EU “so that we would stand tall and have a global vision of what we do.”

As various MPs pointed out, nobody in the House was in favour of genocide. And for those keen to signal that Britain was against such depravity, voting for the Alton amendment was about making that clear.

As far as the Uighurs were concerned, it was also consequence-free, since there is no trade deal with the People’s Republic of China to cancel, regardless of what a judicial body might pronounce.

But was reality the point? MPs on both sides of the House felt that it was the principle that mattered. And as the shadow international trade secretary, Emily Thornberry, posited, just because the current government said it had no intention of signing a bilateral agreement with China did not mean that at some stage in the future there might not be an entanglement. What if Britain joined the trans-Pacific partnership, the CPTPP, as it has mooted doing, and subsequently found itself in whatever trade orbit the CPTPP extended to China?

Indeed, Thornberry did not want it to be imagined that genocide was only something Beijing engaged-in. She also had “deep concerns” about the human rights record of Egypt, Turkey, Cameroon, Saudi Arabia, Bahrain, and Brazil. Even Trump’s administration had cancelled Cameroon’s preferential trade rights because of the African republic’s human rights abuses, she stressed; on the same day the Senate passed a resolution backing-up that revocation with a call for other trading nations to take similar action, the British government brought into effect its continuity trade agreement with Cameroon – the details of which remain unpublished.

It fell to the former international trade secretary, Liam Fox, to imply some of his fellow Brexiteers backing the amendment had taken leave of their senses in wanting to give the power to block or break international treaties to the High Court. “I don’t want to take back control from unelected judges in Europe and give more power to judges in the United Kingdom,” Fox made clear. Ethical decisions should be taken by “elected parliamentarians.”

Duncan Smith duly fought back: it wasn’t as if MPs made trade deals (that was the government’s job, using royal prerogative powers), and if judges struck down such powers then MPs would gain the opportunity to scrutinise any primary legislation a government might introduce to restore a trade deal voided by the High Court. Really, it was a double win for parliamentary sovereignty: taking the moral high ground and clipping government unaccountability into the bargain.

Fox, though, could see “the thin end of the wedge” because “in future trade Bills, we may get amendments on the use of torture or on other human rights violations” and “once we have set a precedent that the court can make a judgment [on genocide] and tell Parliament what it can and cannot do, I wonder how we can reverse that trend?” Indeed, he despaired that, “we talk about taking back control, but parliament has got to stop giving its decision-making powers away.”

we talk about taking back control, but parliament has got to stop giving its decision-making powers away

This cut no ice with Labour’s Stephen Kinnock who asserted it was “nonsense” that the genocide was transferring decision-making from politicians to judges. “It has been the settled policy of UK government for decades that judges, not politicians, rule on genocide.” With admirable patriotism, the Alton amendment “would be empowering, through that amendment, our esteemed British judges to make such a ruling, rather than the judges in an international court.”

Speaking for the government, the trade minister, Greg Hands, endeavoured to remind MPs that, whatever its noble intention, the amendment would make for seriously bad law.

Quite how problematic was made clear by the former attorney general, Jeremy Wright. For the High Court to make its preliminary determination, alleged victims of genocide would first have to take their case to it. And here was the flaw. “The amendment sets out who could bring an action, but not who the respondent would be,” Wright pointed out. “It is hard to see the respondent being the foreign government in question. Would it be the UK government instead, and if so, how would they present a case about the behaviour of a foreign government, of whom they are likely to have been critical?”

Put like that, it did seem as if tying-up prospective or even active trade deals in months of court hearings, with judges pronouncing on the alleged goings-on in a country over which they had no legal jurisdiction, was not as simple as its proponents made it sound.

“I am a barrister,” Sir Edward Leigh reminded his colleagues. “Do we really think,” he postulated, “that, if we accused any country—China, Saudi Arabia, Israel, Turkey, Egypt—they would agree for a moment to send counsel to defend their position?” Indeed, since what goes around comes around, might they encourage their own courts to pronounce on Britain’s human rights record in Northern Ireland – “what would we think if we were going to do a trade deal with somebody and some group took us to court in, say, Japan? Would we ever turn up in some Japanese court and defend our position? No, we would think that that would be a fundamental denial of the supremacy of this Parliament.”

But when the House divided, rejecting the Alton amendment by 319 to 309, the narrow margin of the government’s victory suggested that for many legislators this was a vote about their principles, not the legal practicalities. The problem is that MPs are lawmakers.