The Supreme Court handed down its judgment on 31 October 2012.
Mr Rahmatullah was detained by UK forces in Iraq in 2003 and handed over to US forces, subject to a Memoranda of Understanding on the transfer of detainees. He has been held in Afghanistan at Bagram Airbase since some time in 2004. Supported by Reprieve, his family sought habeas corpus, and the writ was subsequently granted by the Court of Appeal. Although the writ was discharged, following the production of further correspondence between UK and US diplomats, the UK Government pursued an appeal to the Supreme Court to argue that the Court of Appeal had no jurisdiction to act. Mr Rahmatullah cross-appealed.
JUSTICE intervened in this case principally to argue against a narrow interpretation of the jurisdiction of habeas corpus and to highlight the inconsistency between the Government’s submissions in this case and their wider use of Memorandum of Understanding for the purposes of allowing return of individuals to States where they may face a real risk of torture.
Unanimously, the Court rejected the Government’s appeal. It also rejected the cross-appeal (JUSTICE did not make submissions on the factual issues in the cross-appeal).
Lord Kerr, giving the lead judgment, concluded:
An applicant for a writ of habeas corpus must therefore demonstrate that the respondent is in actual physical control of the body of the person who is the subject of the writ or that there are reasonable grounds on which it may be concluded that the respondent will be able to assert that control. In this case, there was ample reason to believe that the UK Government’s request that Mr Rahmatullah would be granted. Not only had the 2003 MOU committed the US armed forces to do that, the government of the US must have been aware of the UK government’s view that Mr Rahmatullah was entitled to the protection of GC4 and that, on that account, it was bound to seek his return if (as it was bound to do) it considered that his continued detention was in violation of that Convention. 
Baroness Hale and Lord Carnwath would have allowed the cross appeals and gave dissenting judgments on these issues. Both Lord Phillips and Lord Reed gave separate judgments in which they expressed some reservations about some parts of the majority decision.
The Court’s judgment is available here