According to both Article 51 of the UN Charter and related customary international law, occurrence of an ‘armed attack’ is required for the activation of the inherent right of self-defence. The ICJ identified ‘scale and effects’ as the criteria that ‘distinguish the most grave forms of the use force (those constituting an armed attack) from other less grave forms,’ but has not specified indicators of these criteria (Nicaragua judgment, 1986, para. 191). It should be noted that the scale and effects criteria have nothing to do with numbers. Rather, it is a legal assessment depending on facts and circumstances at hand.
Some scholars, such as Peters and Talmon, are sceptical that the terrorist attacks occurred prior to the launch of Operation Olive Branch. Their suspicion is understandable, as it is the burden of the victim State to provide substantiating evidence of the factual occurrence of an armed attack (Armed Activities judgment, 2005, para. 146). Turkey should therefore have substantiated the YPG’s attacks and their consequences in its letter to the UN Security Council. Turkey still has the opportunity and burden to convince the international community in this regard.
In its letter to the UN Security Council, Turkey indicated that Operation Olive Branch was initiated to respond to the recent increase in the PKK/YPG’s long-standing attacks and to counter terrorist threats from Syria. Turkey’s military actions and legal position in this respect seem to be in line with the practice and legal positions of some States such as Australia, Canada, the UK and the US, which justified their use of force in Syria on the basis of an individual or collective right of self-defence to respond to terrorist threats or imminent armed attacks. Peters rightly expresses her concern that opening the door of self-defence to ‘the threat of terrorism’ may trigger abusive invocations of self-defence. Likewise, it should be kept in mind that the requirement of imminence is more likely to be satisfied with evidence of a perpetrator’s concrete plan to launch an armed attack rather than just the mere capability to launch one in future. However, what Turkey argues here is not only the general threat of terrorism or mere capacity of a non-State actor: Turkey points directly to the propensity of the PKK and its affiliates to launch attacks when conditions are suitable. In other words, Turkey has considered the recent increase in the PKK’s long-standing attacks and concluded that it represents a permanent and active threat of further attacks, both in terms of capacity and intent.
Whatever they name themselves, this kinship seems sufficient to categorize the PYD/YPG as a Syrian wing of the PKK. The YPG has taken advantage of the conditions of the instability in Syria and expanded its control over the areas in northern Syria alongside the Turkish border thanks to extraordinary US military support, repeatedly condemned by Turkey. Under these circumstances, had it not launched this military operation, Turkey may have lost the opportunity to defend its border security effectively. In other words, failure to stop the advance of the YPG along its border today would reasonably be expected to result in the YPG’s larger-scale attacks against Turkey in near future.
That view is also shared by Turkey as it launched Operation Olive Branch to stop the advance of the YPG and its terror corridor in northern Syria before it loses the opportunity to defend itself effectively.
Although there is significant legal uncertainty over the question of whether an armed attack by a non-State actor not attributable to a State suffices to trigger self-defence (for this discussion, see Milanovic’s article), State practice in the wake of 9/11 has started to evolve in the direction of affording States the right of self-defence in response to attacks conducted by non-State actors. This evolution is, in fact, not contrary to the UN Charter, as nothing in the language of Article 51 limits ‘armed attack’ to attacks attributable to a State. Accordingly, as has been embraced by some States, such as Australia, Canada, Germany, Turkey, the UK and the US, when the host State is ‘unable or unwilling’ to prevent its territory being used as a base for launching attacks against the victim State’s territory, the victim State is permitted to exercise its right of self-defence providing that its requirements are met.
The ICJ, however, has not embraced this approach yet (Wall advisory opinion, 2004, para. 139; Armed Activities judgment, 2005, para. 147). In line with the jurisprudence of the ICJ, many scholars, such as Heller and Green, argue that there is no consistent State practice supporting the ‘unable or unwilling’ test in relation to self-defence actions adopted against non-State actors.
The willingness of subjects of international law to apply the right of self-defence against non-State actors can be observed by the recognition of the US right to respond in self-defence against the 9/11 attacks (see Paust’s article). I think, in the face of such recognition by the Security Council, NATO as well as majority of States, international courts and scholars should have been prepared to review their traditional approach. Otherwise, giving this right to one State but not to others would be a double standard, violating the understanding of the equality of States enshrined in Article 2(1) of the UN Charter and undermining the international legal order.
In accordance with customary international law, the ICJ confirmed that two more criteria, proportionality and necessity, need to be met for a lawful exercise of self-defence (Nicaragua judgment, 1986, paras. 176, 194; Oil Platforms judgment, 2003, paras. 43, 73-74, 76).
The scale, scope, duration and intensity would be determinant factors in an assessment of the proportionality of any self-defence action. Turkey should, therefore, exercise its military operation in accordance with the statements of Turkish officials emphasizing its temporary nature and limited purpose of clearing its border from terrorist organizations.
As to necessity, the US has been warned by Turkey several times in recent years for its increasing military support to the YPG by providing heavy weapons, training its fighters and even planning to create a so-called ‘Border Security Force’. This support has increased the YPG’s military capacity in Afrin, triggering Operation Olive Branch. Given this growing capacity, no less intrusive means remain available to Turkey to defend its national security interests aside from conducting an extraterritorial military operation against the YPG.
Congratulations, for this detailed discussion. In the last section, however, you said: “Turkey should, therefore, exercise its military operation in accordance with the statements of Turkish officials emphasizing its temporary nature and limited purpose of clearing its border from terrorist organizations”. I think it could be better if you evaluate the indiscriminate operations (attacks without distinction between civilian and military objectives) by Turkey in the region which had been led to the displacement of a large number of the indigenous people.
Thanks for your comment. Since I already exceeded the word limit, I did not have the opportunity discuss the proportionality and necessity requirements in detail. In addition, the focus of the post is jus ad bellum. However, had I had an opportunity to analyse the operation under jus in bello, my approach would have been different from yours.
The principle of distinction is one of the cardinal principles of IHL and requires parties to an armed conflict to distinguish peaceful civilians from members of organized armed groups and those taking a direct part in hostilities. You are rightly drawing attention to this and respect for rules of IHL. There is no doubt that Turkey is obliged to carry out its military operation in compliance with this principle. However, one should also be aware that there are countless examples of fake images and misleading information on social media (https://twitter.com/trtworld/status/960381233875140608). The factual issues are subject to political manipulation at the moment and everyone should be careful about claiming that it is the reality on the ground.
I would recommend you take also following points into consideration before labelling Turkey’s military operation as a violation of IHL.
1- Parties to a conflict have the obligation to remove civilians and civilian objects under their control ‘from the vicinity of military objectives.’ However, Turkish army drones have captured on film the YPG/PKK’s attacks on Turkey’s border provinces from between houses in residential area inside Syria. Following the rocket attacks, militants are seen fleeing to nearby houses. (http://www.hurriyetdailynews.com/drones-capture-ypg-attacks-on-turkey-from-syria-127266). One should keep in mind that allowance of intentional misuse of the law’s protective provisions creates a great risk that respect for IHL will be undermined. Therefore, an armed group taking military advantage via violating rules of IHL by using civilian persons and objects as shield, in fact, undermines IHL itself.
2- Civilians are all those who are not members of organized armed groups whether State or non-State in character and they are protected against attack, unless and for such time as they take a direct part in hostilities. So make sure that persons you are talking about remained civilians, not took a direct part in hostilities (https://twitter.com/julianroepcke/status/960798254471503872).
3- Lastly, what is prohibited under IHL is to launch an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated. The term ‘excessive’ implies a higher threshold than ‘extensive’ or ‘disproportionate.’ If Turkey may prove that it has taken constant care to spare the civilian population, civilians and civilian objects and all feasible precautions to avoid, and in any event to minimize, incidental loss of civilian life, injury to civilians and damage to civilian objects, the operation remains lawful even though it causes incidental loss that is not excessive.
Thanks for this note. I don’t see much relevance to burden of proof. It’s only relevant in judicial proceedings. Because self defense is the exception to the prohibition on the use of force, the side arguing for self defence in a judicial proceeding bears the risk of losing the case if it doesn’t prove it. But that is different from saying that a state has an obligation generally under international law to prove it has a right to resort to self defense (and not just a reporting obligation to the SC). There is nothing in state practice supporting an obligation like that.
Turkey does have the burden of proof in its report to the Security Council. It is arguing that it is justified in violating Article 2(4) because its actions meet the terms of lawful self-defense. It needs to meet the burden with clear and convincing evidence.
As for what the terms of lawful self-defense are, a small group of states willing to use force against non-state actors regardless of the conditions of armed attack, necessity, proportionality, and state responsibility cannot modify the peremptory prohibition on the use of force.