We should have seen this coming. It was patent from the start that last year’s ‘one in, one out’ agreement with France was a toothless pact designed for show, that left all the immigration cards in France’s hands and most of the more undesirable would-be migrants in ours. We could also have foreseen that a sniping lawfare campaign against even this limited effort would start then and there. And so it proved. This week, Mr Justice Sheldon in the High Court peremptorily stopped the removal to France of three boat arrivals who, rather implausibly, alleged that they had been trafficked.

The details are boringly legal, but they matter. Any irregular arrival who claims to stay on the basis that they are the victim of modern slavery or trafficking is immediately interviewed. If the officer determines there might be reasonable grounds to believe them, they get a very temporary right to stay while the matter is investigated. If the interviewer decides there are no reasonable grounds to believe them, their trafficking case is shut out. Until the ‘one in one out’ scheme, official Home Office practice provided a right to reconsideration of any ‘no reasonable grounds’ decision: but because of the tight timing under the new arrangement, the right to a second opinion was removed.

This, said the judge, was unjustifiable. Tired, disoriented and perhaps traumatised arrivals could not be expected to make their slavery case without some leisure to construct their story and demand another chance. The Home Office had therefore acted unlawfully.

Apart from the fact that it scuppers much of the ‘one in one out’ arrangement, this decision – which, incidentally, is legally pretty impeccable – is disconcerting. It was based, not on human rights, but on two other things: the provisions of the Modern Slavery Act 2015, and a 2009 treaty called the European Convention against Trafficking. True, neither said anything expressly about the right to a second opinion when a modern slavery allegation was declared hopeless. But no matter. There could be divined from each of them, it was said, an underlying intention to ensure that anyone alleging trafficking had the right to sufficient time to put their case in the most convincing way. Since they had not had this, the new rules could not be applied.

Like it or not, the law has its predilections, imbued through precedent. And whereas in national security cases the system leans very much in favour of executive efficiency over individual rights (witness the recent sustaining of the ban on Hamas), in immigration and refugee cases (one suspects because the law is largely developed by immigration practitioners with liberal beliefs on border issues) priority very often goes to the interests of the would-be migrant and any doubt is resolved in his favour.

For any country that needs strict and at times summary control over who crosses its borders, this won’t do. But what should the conservative response be? Attacks on the judiciary, or calls for its reorientation or replacement with those of a different mindset, are obviously out. We don’t do things that way, and in any case in a democracy two can play at that game.

There are nevertheless three policies that any decent right-leaning opposition party needs to put forward to deal with the matter (quite apart from a pledge to denounce the ECHR, which is rightly already in both Tory and Reform manifestos, but which would not have made a difference here). First, it must call for the UK to avoid signing instruments like the Convention against Trafficking. Such virtue-signalling conventions do us no good, and can (as happened yesterday) come back to bite us by skewing the interpretation of our own law. Secondly, it must pledge to draft all future immigration legislation meticulously, so as to give as little room as possible for ambiguity and suggestions of a presumed intention to favour would-be immigrants’ rights. And thirdly, any opposition must promise to have no compunction about stating expressly that legislation is intended to operate independently of particular alleged civil or human rights.

This is a policy that should go down very satisfactorily with voters from Blyth to Billericay feeling fed up with the pretensions of this hapless government.