The legality and enlightenment of preventive self-defence in international counter-terrorism

Abstract In international counter-terrorism practice, whether states can exercise preventive self-defence against the imminent threat of international terrorist attacks has been a controversial topic. From the perspective of international treaty law, Article 51 of the United Nations Charter hardly constitutes a direct legal basis for preventive self-defence in international counter-terrorism. However, from the perspective of international customary law, empirical analysis shows that the representative preventive self-defence practices of several states after 1945 have met the requirements of consistency, generality, representativeness, and temporality, thus forming international customs. Moreover, states have developed opinio juris regarding preventive self-defence, thus leading to its evolution into a rule of modern international customary law, thereby conferring legality on preventive self-defence in international counter-terrorism. Given the risk of abuse of preventive self-defence measures in international counter-terrorism and its severe challenge to the national sovereignty of the state where terrorist organizations are based, its application must comply with substantive conditions such as severity, authenticity, urgency, and proportionality, and must adhere to procedural conditions of obtaining the consent of the host state, to be deemed lawful. Only in this manner can a balance be maintained between the international rule of law and the need to combat terrorism.