15 September 2015
Further clarification is needed on the legal justification for the UK’s drone strike in Syria. Greater transparency is ultimately in the government’s interests.
Harriet Moynihan

Harriet Moynihan

Associate Fellow, International Law Programme


A US Reaper drone comes in for a touch and go landing during a training programme for pilots. Photo: Rick Loomis/Los Angeles Times via Getty Images.
A US Reaper drone comes in for a touch and go landing during a training programme for pilots. Photo: Getty Images.


The UK government has asserted the right of self-defence as the legal justification for its drone strike in Syria, but the application of this and other rules of international law needs further clarification. Greater transparency is also needed, given the change of policy direction and the importance of public and parliamentary confidence in the government’s use of drones.

On 7 September, Prime Minister David Cameron announced that a UK drone had killed three members of Islamic State of Iraq and Syria (ISIS) in Syria, two of whom were British nationals. He stated that there was no other option to protect the UK from imminent armed attacks, and that the attorney general had confirmed that there was a clear legal basis to act. 

The targeting of ISIS fighters in Syria marks a change in direction by the government, which to date has been tackling the terrorism threat to the UK by and large under the criminal justice model – that is, by prosecution and trial. The government justified military action against ISIS in Iraq as being for the collective self-defence of Iraq, and with Iraq’s consent

But the widening of UK action against ISIS into Syria requires its own legal justification, which in turn depends on defining the nature of that action. Was the drone attack in Syria an act of self-defence in the face of a threat of imminent attack on the UK – and if so, did it take place within the framework of an ongoing armed conflict against ISIS fighters or was it an action of law enforcement against individuals involved in terrorism? If it was the latter, is it lawful to target individuals in this way?


The criteria governing the right to use force in self-defence under Article 51 of the UN Charter are that the threatened attack is imminent, and that the act of self-defence is both necessary and proportionate. In its letter of 7 September 2015 to the UN Security Council, the government states that these criteria are met.

The exercise of self-defence in this case is not against a state but against an armed group, which brings its own legal difficulties. Although not uncontroversial, an argument can be made that military action against armed groups, without the consent of the state in which they are to be found, is lawful if that state is unable and unwilling to prevent the armed groups attacking other states. But the criteria for self-defence in such a case must be strictly applied. The 2005 Chatham House working paper entitled Principles of International Law on the Use of Force by States in Self-Defence suggests that only in the ‘most compelling emergency’ could it be justified for the threatened state itself to take military action in self-defence before an attack is launched. One of the difficulties in assessing situations like this is that the lawfulness will depend on the evidence. The government will continue to be asked for further information.

An armed conflict or law enforcement?

There seems to be confusion as to whether the UK government regards itself as being in an armed conflict with ISIS. The government’s letter to the Security Council refers to the ongoing armed attacks by ISIS against Iraq, and seems to link the strike to the existence of an armed conflict. However, the prime minister himself stated that ‘this strike was not part of coalition military action against ISIL in Syria’

If the strike were part of an existing armed conflict, international humanitarian law would apply, including rules on targeting which permit the killing of fighters in a ‘non-international’ armed conflict. But one military strike in self-defence does not give rise to the intensity of action required to meet the threshold for a non-international armed conflict. For an isolated act of self-defence, only human rights law applies. That law sets a very high threshold before the taking of life can be justified: the threat to others must be immediate (as in a policing operation). It is not unreasonable that human rights law should constrain such actions. No one can expect that governments may kill individuals outside armed conflict without legal regulation.

Greater transparency

The Iraq war left the public, parliament and civil society with a lack of faith in the UK’s use of intelligence as the basis for controversial military actions. The UK’s change of direction against ISIS in Syria has sparked calls from many commentators for greater clarity on the government’s position, and for disclosure of the legal advice it has received.

While the government cannot be expected to release confidential intelligence information, some form of greater transparency on the application of the relevant legal criteria would help to reassure parliament and the public that the assessment process is sound and made in good faith. More transparency in this area could also lessen the likelihood of such attacks encouraging more people to join terrorist groups in the UK or elsewhere. On a broader level, it is important to reassure the public that drones – which are set to become an integral part of the UK’s military capability – are being used within a framework of rigorous scrutiny and established procedures.

There is a range of options for greater transparency that would fall short of disclosing intelligence or the full advice of the attorney general. These include publication of a summary of the legal advice (as with the Iraq war); scrutiny of the decision by a parliamentary body such as the Intelligence and Security Committee; or review by other security-cleared officials such as privy counsellors or the UK’s independent reviewer on counterterrorism, David Anderson QC. Improving public and parliamentary confidence in the legal basis for strikes may also strengthen the government’s hand in any future vote on military action in Syria. 

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