Mother of suspect is challenging UK decision to assist US without seeking assurances men will not face death penalty

The Isis terrorist suspect and former British citizen El Shafee Elsheikh has no enforceable rights under human rights legislation or common law in the UK, the high court has heard.

Elsheikh, who is facing extradition to the US, where he could be sentenced to death, has been “assessed” to be a Sudanese citizen, Sir James Eadie QC, for the Home Office, told the court on Tuesday.

Elsheikh, who was stripped of his British citizenship in 2014, is being held by Syrian democratic forces in Syria, Eadie said. “[He] chose to go to Syria. He is suspected of involvement in the beheading of British, American and Japanese [hostages].”

Eadie said: “The seriousness of the crimes is at the apex of the seriousness of crimes. For that reason there’s the most powerful interest in the investigation of these crimes and the trial of those involved.”

Elsheikh and Alexanda Kotey, who both were raised in Britain, are alleged to have been part of an Isis terrorism cell, some of whom were known as “the Beatles”, which is thought to have carried out 27 beheadings of US and UK citizens in Isis-held territory. Those killed included the British aid workers Alan Henning and David Haines and the American journalists James Foley and Steven Sotloff.

The pair were captured in February by Syrian Kurdish fighters, prompting behind-the-scenes negotiations between the UK and the US governments over where they should be prosecuted.

Maha El Gizouli, Elsheikh’s mother, is challenging the Home Office’s decision to provide mutual legal assistance to US prosecutors without seeking assurances from the US that the two men would not face the death penalty – the approach taken by previous home secretaries, including Theresa May.

Eadie said: “There’s no domestic authority which establishes that the government is under an obligation not to provide mutual legal assistance to a friendly foreign state which is governed by the rule of law and which [has] the death penalty.”

No such prohibition applies under the EU charter, Eadie added, while Elsheikh, who is no longer a UK citizen and is in Syria, is beyond the jurisdiction of the European convention on human rights.

The high court has heard that the security minister Ben Wallace, the home secretary, Sajid Javid, and the former foreign secretary Boris Johnson, all approved the decision not to seek assurances from the Trump administration that Elsheikh and Kotey would not face the death penalty.

Judgment is expected to be reserved to a future date.