The use of drones to kill UK citizens has been called unlawful by the Green Party’s MP Caroline Lucas and Baroness Jones, who are seeking a judicial review of the policy.
David Cameron told MPs in his statement on 7 September that the strike had been approved at a meeting of the most senior members of the National Security Council and authorised by defence secretary Michael Fallon.
He claimed the country acted under Article 51 of the United Nations charter, which preserves the “inherent right of individual self-defence if an armed attack occurs against” a member, citing that British security forces had foiled six attempted terror attacks in the UK in the past year.
Parliament had not authorised the attacks, which were the first targeted UK drone attacks on British citizens.
In the letter to the Ministry of Defence, Ms Lucas and Baroness Jones argue that the government has not formulated a policy, or failed to publish it, and in their view either situation is unlawful.
The letter reads:
If any pre-authorised and targeted killing can be lawful, they must be carried out under a formulated and published Targeted Killing Policy which ensures transparency, clarity and accountability for such use of lethal force.
The calls have the support of Reprieve, an international human rights charity, which told the BBC that the government’s justification of the strike "effectively claimed the power to kill anyone, anywhere in the world, without oversight or safeguards".
Labour has called for the attorney general’s advice to be published.