University of Tehran Public Law Studies Quarterly 2423-8120 55 4 2025 12 22 Criteria for Determining an Unwilling or Unable State under Customary International Law Criteria for Determining an Unwilling or Unable State under Customary International Law 2323 2346 102869 10.22059/jplsq.2024.373553.3531 FA Alireza Norouzi Ph.D. Student in International Public Law, Faculty of Law and Political Science, Azad Islamic ‎University of Qaemshahr, Qaemshahr, Iran‎ Iraj Rezaeenezhad Assistant Prof., Department of International Public Law, Faculty of Law and Political Science, Azad Islamic University of ‎Chalus, Chalus, Iran Karan Rohani Assistant Prof., Department of International Public Law, Faculty of Law and Political Science, ‎Azad Islamic University of Qaemshahr, Qaemshahr, Iran‎ Journal Article 2024 06 10 Since ancient times, non-state actors, such as terrorist groups, have caused widespread suffering in the world, resulting in governments becoming victims of their attacks. These states have faced an unprecedented legal dilemma regarding how to confront and respond to non-state actors within the territory of another state. When the host state is not legally responsible for the attacks, the use of force by the victim state against a non-state actor within the host state’s territory may result in a violation of the host state’s sovereignty and territorial integrity. According to the “unwilling or unable” standard, if the territorial state is unwilling or unable to control threats posed by non-state actors, the victim state may resort to force within the host state’s territory without obtaining its consent. Consequently, this standard diverges from existing legal requirements and significantly lowers the threshold of the prohibition on the use of force. This paper, employing a descriptive-analytical method, addresses the question: Can the “unwilling or unable” standard be considered a constitutive norm of customary international law? The study concludes that, although this standard—and, by extension, the right to self-defense against non-state actors—receives some support among legal scholars, it has not generally been accepted as customary international law due to reasons such as the lack of state practice, the subjective element, extensive criticism, and non-acceptance by the international community. Since ancient times, non-state actors, such as terrorist groups, have caused widespread suffering in the world, resulting in governments becoming victims of their attacks. These states have faced an unprecedented legal dilemma regarding how to confront and respond to non-state actors within the territory of another state. When the host state is not legally responsible for the attacks, the use of force by the victim state against a non-state actor within the host state’s territory may result in a violation of the host state’s sovereignty and territorial integrity. According to the “unwilling or unable” standard, if the territorial state is unwilling or unable to control threats posed by non-state actors, the victim state may resort to force within the host state’s territory without obtaining its consent. Consequently, this standard diverges from existing legal requirements and significantly lowers the threshold of the prohibition on the use of force. This paper, employing a descriptive-analytical method, addresses the question: Can the “unwilling or unable” standard be considered a constitutive norm of customary international law? The study concludes that, although this standard—and, by extension, the right to self-defense against non-state actors—receives some support among legal scholars, it has not generally been accepted as customary international law due to reasons such as the lack of state practice, the subjective element, extensive criticism, and non-acceptance by the international community. https://jplsq.ut.ac.ir/article_102869_b4a95e1777ef693d93c96da6b8249c81.pdf