Prime Minister Tony Abbott has acknowledged that there is “a little difference” between the legalities of air strikes in Syria and in Iraq against Islamic State (IS) forces.

Australia currently conducts airstrikes against IS in Iraq with the Iraqi government’s consent. But Australian air combat missions in Syria – which loom after a formal request from the US government for Australia to expand its role into Syria – would be in a legal grey area.

Self-defence and the UN

The UN Charter allows an exception from the prohibition on the use of force only for collective and individual self-defence in response to an armed attack and for use of force authorised by the UN Security Council.

But, Australia has no case for self-defence. IS has not made an armed attack on it. Russia and China would likely veto Security Council authorisation for the use of force against IS in Syria.

Australia could claim that it is exercising the right of collective self-defence, in response to IS attacks in Iraq, along with the US and other nations. But the International Court of Justice has said in several cases – most controversially in its 2004 advisory opinion on the legality of the wall between Israel and Palestine – that the Charter right of self-defence only applies to an armed attack by another country, not a non-state actor.

Several judges of the court have disagreed. UN Security Council resolutions 1368 and 1373, adopted after September 11, recognised a right to self-defence against terrorist attacks.

Australia could therefore argue that the right of self-defence should apply against the territory of a country that assists or harbours the terrorist group. Syrian opposition groups say that the Assad régime and IS are tacit allies in a common war against the secular Free Syrian Army and other Islamist groups.

This is at least partly true. However, these claims would fall short of the necessary evidence to show that the Assad régime is assisting or harbouring IS.

Islamic State as a ‘state’

An alternative argument, advanced by the US and supported by Australian Foreign Minister Julie Bishop, is that the IS-occupied area of Syria is “ungoverned space”. The US State Department defines ungoverned space as:

… areas of a country and non-physical areas where terrorists are able to organise, plan, raise funds, communicate, recruit, train, and operate in relative security because of inadequate governance.

The State Department has referred to the area IS controls as:

… large swaths of ungoverned space inside Syria that [it] has been able to take advantage of and to exploit.

However, the IS-controlled area of Syria is governed – harshly and comprehensively – by IS. A number of commentators argue that IS is, or is on the verge of becoming, what it claims to be: a state. Yale University’s Andrew March and Mara Revken have shown that IS is “creating a distinctive and authentic legal order” based on a long-standing Islamic theory of statecraft. IS is establishing law-based governance of all the functions of a state, from traffic fines to environmental protection.

The US has transferred the rationalisation of “ungoverned space” from the war against al-Qaeda to the fight against IS. But IS is not fundamentally a terrorist organisation. As military strategist David Kilcullen says, IS is “fundamentally a state-building exercise”. Bishop’s application of the concept of ungoverned space to IS is a fiction.

International law recognises facts, however contrary to international legal norms, under the principle of effectiveness. International law cannot comprehensively identify and punish violators of legal norms in the way that domestic legal systems can. So, it adapts to factual situations rather than spinning convenient fictions.

Abbott would not want to extend the legitimacy of statehood to the IS “death cult”, but this would provide a fact-based justification for Australian air combat operations in Syria against IS. IS, as a “state”, has attacked Iraq, which has appealed to Australia and other states to fight IS under the UN Charter right to collective self-defence.

Australian air attacks against IS targets in Syria would not be definitely legal but not definitely illegal. This lacks the impact of other three-word slogans. But if Abbott wants to say “yes” to the US’ request for Australia to join the air attack against IS in Syria he will have to settle for it.