Abstract
Critics of the unwilling or unable doctrine suggest that it could undermine the United Nations collective security system and argue that it requires an unacceptable ceding of a State’s territorial sovereignty. Increased reliance on the doctrine following the terrorist attacks of 9/11, particularly in relation to the use of force against ISIL in Syria since 2014, has caused the doctrine to face significant scrutiny. The purpose of this article is to ascertain whether the unwilling or unable doctrine has reached customary international law status. If found to be the case, the doctrine would confirm the right of States to act in self-defense when an extraterritorial armed attack cannot be attributed to a State, and where the territorial State is not willing or able to address the threat posed by the non-State actor. The article concludes that there is sufficient relevant State practice and opinio juris sive necessitates to conclude that the doctrine has reached customary international law status. It finds that while controversy regarding its application remains, the basic desire of States to protect themselves is such that continued reliance upon the doctrine is inevitable.
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