A human rights group has begun legal action to force the government to reveal the advice it received from lawyers justifying the killing of British jihadis in Syria.



The move by Rights Watch (UK) comes as critics said the threat by Michael Fallon, the defence secretary, to target other militants overseas was comparable to a US-style “kill list”.

Fallon’s promise that the government “wouldn’t hesitate to take similar action again” against “other terrorists involved in other plots” raised fresh questions about the legality of the government’s policy.

David Cameron announced on Monday that two British citizens, Reyaad Khan and Ruhul Amin, had been killed in an RAF targeted strike. A third Briton, Junaid Hussain, was killed in a US operation acting jointly with UK intelligence.

The prime minister told MPs it was legally justified as an act of self-defence because the threat they posed to life in the UK was “imminent”.

On Tuesday Downing Street conceded that a list of names of several British jihadis had been drawn up at the meeting of senior national security council members that approved the drone strike that killed Amin and Khan.

The father of two young men believed to be fighting for Islamic State in Syria, one of whom went to school with Khan, has said he worries they could be targeted next.

Ahmed Muthana said he feared that his sons Aseel, 18, and Nasser, 21, were at risk from further strikes. “I am frightened because my sons are out there too,” he said. “I worry that they could be on a hitlist. I don’t think I will ever see my sons again.”

Aseel Muthana (left) and his older brother Nasser. Photograph: Social Media

Lawyers critical of the attack near the Syrian city of Raqqa on 21 August accused ministers of stretching long-established legal definitions setting out what constitutes an imminent threat to a country and its permissible acts of self-defence.

The Obama administration in Washington is already facing legal action over what critics claim is a “kill list” of suspects deemed to be terrorists operating abroad who can be targeted in drone strikes. There is speculation that Mohammed Emwazi, 27, nicknamed Jihadi John, who has beheaded hostages in Isis videos, is likely be among those to whom Fallon was referring.

The government relied on article 51 of the UN charter, which guarantees a state’s right to self-defence. The way in which it is enforced depends on principles formulated in an 1837 court case known as the Caroline test.

That year British forces in Canada crossed the border into the US, seized a steamboat called the Caroline – which was being used to supply anti-colonial rebels in Canada – set it on fire and dispatched it over Niagara Falls.



The British argued that their response was legitimate. The case established that force can be used only if a threat is imminent and pursuing peaceful alternatives is not an option. The response to the threat must be proportionate. Those principles were subsequently upheld in the Nuremberg war crimes tribunals.

Intense political pressure to redefine the Caroline test, however, has come from the US in the aftermath of the 9/11 attacks. A leaked internal US white paper on the “lawfulness of lethal operations”, released in the wake of the killing of a US citizen, Anwar al-Awlaki, in Yemen in 2011, radically revised the concept of imminence.

It stated: “The condition that an operational leader present an imminent threat of violent attack against the United States does not require the United States to have clear evidence that a specific attack on US persons and interests will take place in the immediate future.”

Defence secretary Michael Fallon warns that the UK could launch more drone strikes in Syria. Guardian

Jennifer Gibson, a lawyer at the UK civil rights group Reprieve, said she was concerned that the UK government now appeared to be adopting the US’s much looser definition of imminence than in the original Caroline test.



“The US took the definition of imminence and turned it completely on its head,” Gibson told the Guardian. “Imminence was no longer imminent but rather sometime in the future and with no clear evidence required.

“The question for Cameron now is: which definition is he following? Has the UK also redefined imminence? Did imminence even figure into the equation? Fallon is implying there’s a ‘kill list’. He’s not calling it that but he’s saying there are people in Syria and other places that he’s considering launching strikes against. Having a kill list defeats the claim of imminence.”



In an attempt to expose the government’s legal justification to scrutiny, Rights Watch (UK) has initiated legal proceedings against the government over its refusal to publish the legal advice given by the attorney general, Jeremy Wright QC, to ministers before the attacks were approved.

Unless the government decides to publish the advice within the next seven days, Rights Watch (UK) has said it will issue judicial review proceedings in the high court.

Yasmine Ahmed, director of Rights Watch (UK), said: “There is insufficient information in the public domain … to know whether the drone strikes that killed three individuals in Syria, including two British citizens, were done lawfully.

“These strikes set a dangerous precedent for UK government activity. The UK government can now kill at will with no oversight. If the only oversight for these actions is internal confidential government legal advice, which the British public never gets to see, that is no oversight at all. To take military action in the name of the British public and not fully inform the public about the legal basis for doing so is undemocratic.”

Ahmed said Rights Watch (UK) would support the families of the dead men if they wanted to bring legal actions for compensation against the government.

In a letter to Cameron on Tuesday, the Labour MP Tom Watson asked the prime minister: “Can you confirm that the ‘Caroline principles’ on standard to trigger the right to self-defence under article 51 of the UN charter have been strictly applied to the use of lethal drone strikes?”

Ken Macdonald, a former director of public prosecutions, said he hoped the remarks by Fallon did not signify the adoption of US targeting tactics. While accepting the principle of self-defence, the Liberal Democrat peer said: “If, however, we are talking about moving towards a US system which means targeting anyone who is a self-professed member of a terrorist organisation, then I’m against that. It would defeat the definition of an imminent attack.



“The worry is that this is being broadened out. What these people were concerned with was planning attacks on VE Day, yet they were not killed until several weeks after VE Day. That’s a concern.”



Sir Keir Starmer QC, also a former director of public prosecutions and now a Labour MP, told the Guardian: “We are entitled to know the rules of engagement now being followed, in particular the threshold being applied for the use of lethal force. Necessity and proportionality are broad words and the more extreme the use of force, the higher the threshold and the greater the need for accountability.”



Both the attorney general’s office and Downing Street said they would not be publishing the advice given to the prime minister. A No 10 spokesman said it was contrary to the Cabinet Office manual to release the text of any legal advice.



The attorney general normally answers questions in the Commons every six weeks. His next appearance before the full house is due in October. Next Tuesday, however, Wright will face questions at a meeting of parliament’s justice select committee.