A recent British drone strike on British citizens in Syria raises troubling legal questions about the use of military force in purported self-defence overseas. In late August, Britain targeted an ISIS member, Reyaad Khan, in Raqqa, collaterally killing two other ISIS members, including British national Ruhul Amin. The strike was followed by a US drone attack on another British citizen, Junaid Hussein, also in Raqqa, involving UK intelligence cooperation.

Amnesty International condemned Khan's killing as a 'summary execution'. British NGO Rights Watch is seeking the disclosure of the UK government's legal advice in the British courts.

British Prime Minister David Cameron claimed that the strike was 'necessary and proportionate for the individual self-defence of the UK'. In particular, Khan and Hussein were allegedly involved in 'actively recruiting ISIL sympathizers and seeking to orchestrate specific and barbaric attacks against the west'. These included plots against public commemorations in Britain, such as by attacking soldiers on Armed Forces Day (in June) and VE Day (in May). 

Cameron argued further that there was no government in Syria that Britain could work with, detaining Khan was not possible and that Khan was committed to further attacks. Britain also said that the drone strike was timed to avoid civilian casualties. 

The strike was not part of the US-led collective self-defence of Iraq against ISIS in Syria (which Australia is now involved in), or a wider intervention in the Syrian civil war. It follows the lead of the US in its letter to the UN Secretary General of September last year, where it claimed a right to use individual self-defence against Al Qaeda in Syria planning attacks on the US.

Under international law, a right of self-defence conventionally exists where one state is committing an 'armed attack' against another state. This orthodox understanding stems from the interpretation, between 1945 and 2001, of Article 51 of the United Nations Charter of 1945.

The British and US drone strikes raise a number of legal difficulties. First, Khan, and ISIS, are not states. However, after 9/11 the international community appeared to accept that a non-state actor (Al Qaeda) may be capable of committing an armed attack giving rise to self-defence in foreign territory (Afghanistan), even where the group is not directed or controlled by the foreign state (namely, the Taliban Government). 

The UN Security Council, for example, acknowledged the US right of self-defence, as did NATO, the Organisation of American States and many countries. The International Court of Justice has not yet, however, endorsed this change, and appeared to discount it in the Israel Wall case in 2004 and the case of Democratic Republic of Congo v Uganda in 2006 – despite criticism of the majority by a few eminent (but all Western) judges. 

There is nonetheless growing international support for the view that self-defence is available where a state is 'unable or unwilling' to suppress a terrorist group on its territory that is committing an armed attack against a foreign state. There is currently considerable international sympathy for the right of Iraq to defend itself against cross-border attacks by ISIS from Syria. 

A second legal issue is much more troubling in the Khan case: whether his conduct can be genuinely characterised as an 'armed attack' on Britain. Again, the orthodox legal approach is restrictive. An 'armed attack' by an irregular armed group must be of the gravity, or scale and effect, of a conventional military attack by state armed forces on another state. Lesser violence, including serious crimes such as terrorism, fall beneath this threshold. 

The attacks of 9/11 were an exception because of their magnitude – thousands of deaths, the mass destruction of civilian buildings and aircraft and serious damage to US military headquarters at the Pentagon. Most terrorism, however, is nothing like 9/11. ISIS attacks on Iraq qualify precisely because they take the form of high intensity, conventional military hostilities – capable of routing the Iraqi army – rather than being isolated or sporadic terrorist violence. 

Khan's urgings to sporadically harm British soldiers on the streets of Britain are obviously incitements to serious crime and terrorism, just as the beheading of Lee Rigby was murder. But they are hardly the stuff of a military scale attack triggering a right of military self-defence. They are not even in the same ball park, unless Khan was masterminding another 9/11.

To so lower the threshold of an 'armed attack' is dangerous and brings acute risks of escalation of international violence. It allows governments simply to bomb criminals, and does away with the distinction between policing and war – as long as the criminal is in an unfriendly country. It invites Russia, Chinas and North Korea to utilise the same rules we claim are lawful.

It also abandons the presumption of innocence, fair trial and the adjudication of guilt by an independent court – and makes the Prime Minister's missiles the judge and jury. This is especially problematic where targeting decisions are based not on evidence admitted and tested in court, to a standard of beyond reasonable doubt, but on secret, probabilistic intelligence assessments that are not independently verified or subject to challenge. Also, parliament in Britain, as in Australia, has no role in authorising or constraining such killings.

A final legal issue is that self-defence classically requires an armed attack to be occurring, or at least imminent, rather than being speculatively possible at some time in the future. Khan was killed some months after the high profile plots were foiled; self-defence cannot be necessary against a past attack that has concluded or a plot that never happened. Britain has not presented evidence that Khan was engaged in a specific current or imminent plot, but has relied on general assertions about the risk he currently poses. Bombing for past crimes reeks of extrajudicial punishment. 

Insofar as the strike was directed at Khan's future or predicted conduct, it moves into the territory of President' Bush's vague doctrine of anticipatory self-defence. On this approach, a person can be killed even where the risk they pose is neither demonstrably 'imminent' nor of the gravity of an 'armed attack'. 

Such attacks are reckless and contrary to international law. They violate the right to life, which it may surprise politicians to know is even enjoyed by our terrorist enemies. They are unbefitting of democracies committed to the rule of law and human rights when countering terrorism.

Photo courtesy of Flickr user Defence Images.