Yunus Rahmatullah is a Pakistani citizen. In 2004 he was captured in Iraq by British special forces, handed over to the US, and rendered to the Americans' prison in Afghanistan. Now, a UK court has found that he is being unlawfully detained, and ordered the UK government to demand his return so he can be released.
This will be interesting. Rahmatullah was handed over under a Memorandum of Understanding which allows the UK to also demand his return. But the Americans are alreay dragging their feet, and may be unwilling to effectively release someone they regard as an "enemy combatant". But if they don't, then they'll be breaking their word to their closest ally. This won't just place any future prisoner transfers in doubt - it would also expose British officials to war crimes charges for breaching the Geneva Conventions.
But its also potentially relevant here. New Zealand troops in Afghanistan have similarly taken prisoners and handed them over to the US. As with the UK, those prisoners are our continuing legal responsibility. Meanwhile, New Zealand courts pay attention to UK precedent because of the close parallels in our legal system. Which means that our prisoners (who remain our legal responsibility, even while in US custody) could similarly challenge their detention, and possibly succeed.