When Donald Trump stood before the US Congress last month to deliver his State of the Union speech, two Britons suspected of bring part of Isil’s brutal execution squad nicknamed “The Beatles” were already in the custody of Syrian rebels.
Their capture adds greater resonance to Mr Trump’s promise that night to keep Guantanamo Bay from closure. “I am also asking the Congress to ensure that, in the fight against Isil and al-Qaeda, we continue to have all necessary power to detain terrorists - wherever we chase them down,” he said.
It means the two men, Alexanda Kotey and El Shafee Elsheikh, could yet be transferred to the notorious Bush-era detention camp from their makeshift cells with the Syrian Democratic Forces.
British authorities have already made clear their opposition. Tobias Ellwood, a defence minister, said yesterday(FRI) it was vital to uphold the rule of law and that the likes of Kotey and Elsheikh should be sent for trial at the International Criminal Court at the Hague.
American authorities have so far been at pains to say nothing has been decided.
Major Adrian Rankine-Galloway, an official at the Pentagon, said: "We are still considering options regarding Elsheikh and Kotey, but rest assured our intention is to hold anyone accountable who commits acts like those they are alleged to have committed."
Each option – including a criminal trial on American soil - comes with political risk at a time when the White House has signalled it is getting tougher on suspected militants captured anywhere around the world. And it is likely to involve a complicated diplomatic dance between the UK and the US with their different criminal systems and political norms.
Mr Trump has called for the death penalty to be imposed on terrorists who have carried out attacks in the US and senior Republican figures have pushed for homegrown suspects to be sent to Guantanamo Bay.
Sebastian Gorka, who served as a strategist to Mr Trump, said it was too early to know exactly how the two prisoners would be handled.
But he said he backed the continuing use of Guantanamo Bay, both for its power to glean intelligence and to keep combatants off the battlefield while the war against international jihad continued.
“You don’t read Miranda rights to a person who has been involved in an attack against an army post in the middle of Iraq or just decapitated an American journalist,” he said. “This isn’t a bank robber or a kidnapper. These are people who are waging irregular warfare against America and her allies, the UK included.”
Any such move could spark diplomatic tension with the UK, particularly if it included the possibility of a death sentence.
Clive Baldwin, senior UK legal adviser for Human Rights Watch, said: “Under UK law and practice the UK government should make representations to try to ensure their nationals do not suffer the death penalty or ill-treatment in other country’s justice systems.”
Some reports suggest that objection may have been removed by stripping them of their UK citizenship although the British government has at the same time made clear that it expects the pair to be treated properly.
Mark Kersten, an expert on international justice at the Munk School of Global Affairs at the University of Toronto, said an ICC trial was possible if the court issued arrest warrants for the men.
“Outsourcing is a part of complementarity and no doubt ICC would like a slice of Syria accountability,” he said, referring to the idea that the international court has jurisdiction when national courts are unable or unwilling to act.
However, Robin Simcox, Margaret Thatcher Fellow at the Heritage Foundation in Washington, said transfer to the International Criminal Court would be politically unpalatable to a US administration that does not recognise the court’s jurisdiction.
“If their citizenship has been removed then all signs are pointing towards a US trial,” he said.
Prosecutors in New York, in particular, have developed an impressive reputation for securing convictions of suspects detained around the world – in Afghanistan, Iraq and even the UK.
The FBI and intelligence services have also developed methods to separately interrogate suspects to first obtain actionable information, before then building a criminal case. Ahmed Abu Khattala, who was convicted by a court in Washington for his role in the 2012 Benghazi attack, was interrogated for five days in a temporary brig aboard a US naval vessel in international waters before being formally arrested and read his rights by FBI officers.
Whatever their final destination, the only certainty for now is that Kotey and Elsheikh will not be left to have a trial at the hands of Syrian rebel forces.