In the post-9/11 zeitgeist, the ever-present fear of terrorism has reignited debate regarding whether a State has the right of self-defence against attacks by non-State actors. As Australia targets non-State actors such as ISIS and Al-Qaeda fighters in self-defence, the legality of such actions in international law must be questioned.

Part 1: The Right to Attack Non-State Actors

Attacking terrorists in another State directly conflicts with two fundamental principles of international law, as stated in Article 2(4) of the UN Charter: territorial sovereignty; and the prohibition on the use of force. The only exception to these is the right to self-defence against an ‘armed attack’, as set out in Article 51 of the UN Charter.

But what exactly constitutes an ‘armed attack’? The International Court of Justice (ICJ) interpreted the meaning of the term in Nicaragua v United States of America. It held that an armed attack must be understood as including ‘the sending by or on behalf of a State of armed bands, groups, irregulars or mercenaries, which carry out acts of armed force against another State of such gravity as to amount to an actual armed attack, or its substantial involvement therein’.

In the judgment, the ICJ attempted to convey that the State must have ‘effective control’ over the individuals carrying out the attacks. The idea that one can only act in self-defence against an armed attack by a State was reaffirmed by the majority decision of the ICJ in the Israeli Wall Advisory Opinion. Thus, Nicaragua puts forward a high-threshold test to attribute an ‘armed attack’ to a State, and the Israeli Wall case reaffirms that self-defence can only be invoked in cases of an armed attack ‘by one State against another’.

If both of these facts are presumed to be valid, then how does a State such as Australia possess the right to self-defence against a non-State actor, without significant involvement attributed to the ‘host’ State?

In her dissenting opinion in the Israeli Wall case, Justice Higgins argued that there is ‘nothing in the text of article 51 that… stipulates that self-defence is available only when an armed attack is made by another State’. She suggested that self-defence may be used in the territory of another State without attribution to that State of an armed attack. This is in line with dissenting views of Judge Kooijmans, who noted that the UN Security Council Resolutions 1368 and 1373 (adopted in the aftermath of 9/11 to reaffirm the threat of terrorism and right to self-defence) indicate a change against this traditional view held in Nicaragua, and signified a ‘new element’ in the law of self-defence.

However, one must attempt to rationalise the idea of trying to distinguish between State sovereignty and Australia’s ability to exercise self-defence against private actors. Every act of self-defence that involves entry into another State is in actuality an exercise of self-defence against that State. To deny this proposition would be to ignore State sovereignty. As many scholars have pointed out, all problems arise if a distinction is to be drawn between an action taken against a State, and an action taken against individuals within that State’s borders. It would be rationalised to mean that the use of self-defence against a State would only include targeting government personnel or infrastructure. In fairness, scholars such as Kimberley Trapp address this point and suggest that this would not happen as States can only act in a way that is necessary and proportionate. However, such reasoning could prove to get out of hand when States that invoke self-defence then proceed to destroy significant State infrastructure (such as during the Israeli intervention in Lebanon), in order to stop the threat.

Thus, Higgins’ belief of not requiring State attribution is infeasible. As Steenerghe proposes, the test of attribution should go only so far as to prove a link between the non-State actor and the ‘harbouring’ State, consisting in at least the inability or unwillingness of the latter to stop the activities of the former. Such requirement does not stem from the responsibility rules but from the condition of necessity contained within the law of self-defence. Accordingly, a response of self-defence by a country such as Australia would only be acknowledged and justified when the harbouring State has failed to stop the attacks from its territory. This does not necessarily have to imply a wrongful act from the State itself.

Part 2: The Scope of the Right

If it is acknowledged that Australia and its allies do have the right to self-defence against non-State actors in the Middle East (with the acts being attributed to the harbouring State) then questions must turn to the scope and extent of this right. Ward indicated that UNSC Resolutions 1368 and 1373 reflect the right of self-defence against non-State actors. Indeed, some scholars have suggested that these resolutions were important in recognising that the 9/11 attacks constituted an attack under Article 51 of the UN Charter, and recognising the inherent right to individual or collective self-defence. However, other scholars assert that the resolutions do not go so far as to justify a broader reading of self-defence. Gregory Maggs argues, for instance, ‘(the resolutions) did not say what the right to self-defence entails. Most particularly, it did not say that al-Qaeda had committed an “armed attack” […] and it did not say that the United States had a right to act in self-defence in response to the attack by al-Qaeda.’ Thus, whilst the resolutions may be seen as a step towards creating a broader right to self-defence, they do not explicitly state this and thus should be treated with wariness.

Whilst the scope of the right of self-defence is controversial, there is universal agreement in international law that self-defence must be both necessary and proportionate. These requirements can be traced right back to the Caroline incident in 1837. This limits the right of self-defence to situations where a real threat exists, the response is essential and proportional, and all other peaceful means of resolving the dispute have been exhausted. However, the question remains as to what in fact constitutes ‘necessity and proportionality’.

Consider the case of the Israeli intervention in Lebanon in 2006. Conflict began when Hezbollah, a non-State actor operating out of Lebanon, launched a minor attack on Israeli forces – killing eight soldiers and abducting two. As a result, Israel undertook a month-long land, sea and air campaign, causing serious damage to Lebanese infrastructure and displacing many of its people. Most States condemned the attacks as being completely disproportionate to the threats posed. However, Israel, the UK and the USA maintained that its action was necessary, since rockets continued to launch from within Lebanese borders. Despite this, other States’ reactions largely disagreed with this interpretation of ‘necessity’. The view was widely held that the large number of Lebanese fatalities was greatly disproportionate to the few deaths of Israelis by Hezbollah rockets. Thus, reaction to Israeli campaigns in Lebanon and Gaza, as well as Ethiopia’s intervention in Somalia, continue to show a restricted view of ‘necessity and proportionality’, rather than the wide view held by the USA, the UK and Israel.

From this, further questions must be asked about the scope of self-defence against non-State actors in relation to anticipatory and pre-emptive self-defence. If no terrorist group has committed a terror attack against Australia (though their sympathisers may have), then does Australia have the right to defend itself against a possibly imminent attack? This area of law is highly controversial. Although Article 51 of the UN Charter admits self-defence when an armed attack occurs, it is disputed as to whether states can exert this right in anticipation of an imminent attack, or to pre-empt an attack before it becomes imminent. The Bush Administration attempted to justify pre-emptive self-defence and widen this view to validate its 1998 air strikes in Afghanistan and Sudan to prevent and deter terrorism. It has had extremely limited support from States (including the UK) and President Obama has left his position on this issue deliberately unclear. Thus, it can be argued that whether the scope of the self-defence right extends to anticipatory defence against imminent attacks remains controversial. Contrastingly, ‘pre-emptive’ self-defence has been largely condemned.

The issue of terrorism post-9/11 has evidently raised many questions surrounding Australia’s right to self-defence against non-State actors. This article has argued that States do indeed have this right. However, it requires attribution of the ‘host’ State for being unable or unwilling to stop attacks from within its territory. The exertion of the right has shown through State practice that the use of self-defence must be ‘necessary and proportionate’ in a narrow scope, whilst the use of ‘anticipatory’ or ‘pre-emptive’ self-defence remains highly controversial. With ever-increasing threats of terror attacks in Australia and across the world, laws regarding the right to self-defence can be seen as, more than anything, a work in progress.

Phillip Alphonse has studied at the London School of Economics, and is a current law student at Macquarie University.