CYIL vol. 8 (2017)

CYIL 8 ȍ2017Ȏ THE USE OF FORCE AGAINST THE ISLAMIC STATE ȍ JUS AD BELLUM ASPECTSȎ of any assistance for the commission of terrorist acts and other violent trans-national organized crimes against a Member State” 128 into its definition of aggression. Since then, the “harbouring theory” seems to be losing in attractiveness. Due to this and also because Syria and Iraq can hardly be suspected of harbouring the IS, this theory has not been invoked by States intervening against the IS and will not thus be discussed in more details here. 5.3.3 States Unwilling or Unable to Suppress Terrorist Groups The third suggestion introduces the so called “unwilling and unable” theory. 129 Under this theory, “States have an obligation to ensure their territory is not used to the detriment of other States. Should non-State groups operating from a State’s territory /…/ conduct an armed attack against another State, the /…/ right to self-defense crystalizes. /…/. If the territorial State is either “unwilling or unable” to prevent further attacks from its territory, the victim State may act defensively against the non-State group”. 130 The “unwilling or unable” theory is the broadest one, as it might encompass the situations covered by the previous theories. It, however, extends beyond them, applying also to cases in which the space is not ungoverned and the State makes an effort to suppress the terrorist groups but does not succeed. Turkey has repeatedly invoked the “unwilling and unable” theory to justify its armed actions against the PKK in Iraq. 131 The Russian Federation used the same argument with respect to its incursions into the territory of Georgia in pursuits of Chechen rebels in 2002 and 2007. 132 In the fight against the IS, the “unwilling and unable” theory has served as the main legal ground for the US and its allies intervening in Syria and relying on collective self-defence. The position is summed up in the US letter to the UN which argues that “States must be able to defend themselves, in accordance with the inherent right of individual and collective self-defence, /…/, when, as is the case here, the government of the State where the threat is located is unwilling or unable to prevent the use of its territory for such attacks. The Syrian regime has shown that it cannot and will not confront these safe havens effectively itself. Accordingly, the United States has initiated necessary and proportionate military actions in Syria in order to eliminate the ongoing ISIL threat to Iraq”. 133 This view has been echoed by Australia 134 and Turkey. 135 Similarly as with the previous theories, the “unwilling and unable” theory is not well-established under international law. Yet, the increasing frequency with which it has been invoked by certain States coupled with the silence (acquiescence?) of the rest of the international community might suggest that the legal landscape is gradually changing and that the “unwilling and unable” theory might become part of international law. Yet, even if this were the case, States acting in self-defence would have to respect not only the traditional criteria of self-defence (proportionality, necessity, immediacy, subsidiarity with respect to the UN collective actions, etc.) but also some additional criteria stemming 128 African Union, Non-Aggression and Common Defence Pact, J January 2005, par. 1(c)(xi). 129 See also CORTEN, Olivier, The ‘Unwilling or Unable’ Test: Has it Been, and Could it be, Accepted?, Leiden Journal of International Law, Vol. 29, 2016, pp. 777-799.

130 ARIMATSU, Louise, SCHMITT, Michael M., op. cit., p. 21. 131 See RUYS, Tom, ‘Armed Attack’ and Article 51, op. cit., pp. 447-471. 132 Ibidem.

133 UN Doc. S/2014/695, op. cit. 134 UN Doc. S/2015/693, op. cit. 135 UN Doc. S/2015/563, Letter dated 24 July 2015 from the Chargé d’affaires a.i. of the Permanent Mission of Turkey to the United Nations addressed to the President of the Security Council, 23 July 2015.

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