After a record long gestation period the Supreme Court today handed down its judgment in Belhaj v Jack Straw & Sir Mark Allen and Rahmatullah (No 1) v Ministry of Defence. The facts at issue in this proceeding are of such an enormity that they are not easy to comprehend—so appallingly were the Mr Belhaj, his wife Mrs Boudchar, and Mr Rahmatullah treated on the assumed facts of the case.

Mr Belhaj and Mrs Boudchar had been detained in Kuala Lumpur in 2004 and then rendered to Libya via Bangkok. They allege that the United Kingdom ‘arranged, assisted and encouraged’ their rendition, as well as conspired in and assisted in torture, inhumane, and degrading treatment inflicted on them. Mr Rahmatullah was detained by British forces in Iraq in 2004 on suspicion of having belonged to a proscribed organization; he was transferred to US custody and detained without charge for ten years.

The question before the Supreme Court was, on the assumption that the allegations were true, whether the UK complicity for unlawful detention and mistreatment abroad at the hands of foreign state officers were properly triable in the English courts. A unanimous Supreme Court found for Belhaj, Boudchar, and Rahmatullah; the government’s appeals were dismissed and the cases allowed to proceed to trial.

The cases concerned the so-called foreign act of state doctrine, whereby a court, being an organ of a sovereign, will refuse to pass judgment on the acts of another. Much ink will be spilled over Lord Mance’s impressive lead judgment on the doctrine, which was to the effect that, whichever conception of foreign act of state under which one subsumes the facts of the case, the question of whether the case is triable falls to be considered on a case-by-case basis, regard being had to the principle of the separation of powers. English law will in that regard take into account whether issues of fundamental rights are engaged. Against this background, the case was found to be one in which English courts can in principle pass judgment.

Interestingly for the present purposes, Lord Sumption developed what he called the category of ‘international law act of state’, a concept pegged to international law which requires English courts not to adjudicate on the lawfulness of the extraterritorial acts of foreign states in their dealings with other states or subjects of other states, owing to the fact that these occur on the plane of international law. But, he said, this doctrine did not necessarily apply simply because the subject-matter of a case may incidentally disclose that a state has acted unlawfully; there is a further public policy exception to the doctrine, applicable in cases of violations of rules of international law which enjoy the status of jus cogens, that is, peremptory norms of international law.

Lord Sumption went on to discuss in detail the definition of the concept of arbitrary detention. He said that: ‘in December 2012, the UN Working Group on Arbitrary Detention, after canvassing states on the question what factors qualified detention as arbitrary in their domestic law, concluded that detention might be regarded as arbitrary in customary international law if it lacked any legal basis, but also in some circumstances even if it did have a legal basis, depending on the reason for the detention and in some cases on its duration: UN A/HRC/22/44, at para 38’ (at [269]).

Against this background Lord Sumption took the view ‘that the irreducible core of the international obligation, on which there is almost complete consensus, is that detention is unlawful if it is without any legal basis or recourse to the courts’ (at [270]). Then he observed that ‘The UN Working Group regarded this irreducible core as jus cogens: loc cit, para 49. In my opinion they were right to do so.’

Lord Mance for his part observed that the pronouncement of the Report was ‘most valuable and important’, ‘likely to influence the development of generally accepted and recognised norms’(at [107]).

As the UN Working Group itself has pointed out, its work leading to the conclusion that the irreducible core of the prohibition against arbitrary detention is a norm of jus cogens character was carried out in close co-operation with Oxford Pro Bono Publico (OPBP).

Over several years OPBP, led in this regard by Dr Liora Lazarus and Dr Eirik Bjorge, worked with Professor Mads Andenas, the Chair of the Working Group in charge of the adoption its work on the topic, in gathering and analysing state practice on this question. This led to the conclusion that there is in international law a jus cogens prohibition of arbitrary detention. This conclusion today received Supreme Court imprimatur.

Many congratulations to OPBP and all its Oxford graduate students who worked tirelessly advancing international law and the work against arbitrary detention!