This chapter analyses the ability of public international law to define and judge acts of global terrorism and asymmetric warfare and, more specifically, whether or not the UN Security Council has the authority to grant collective self-defence following a terrorist attack. To do this, the analysis focuses on the conflict of norms between the protection of state security and compliance with human rights law. Despite conflicting norms within international law concerning terrorism and insurgency post-9/11, it is also an institutional as well as definitional conflict that, in practice, jeopardizes the establishment of an effective multinational counterterrorism approach. Much work has been done on the legal problem of colliding norms as well as the lack of definition of terrorism in public international law. However, contemporary approaches to overcome the norm conflict inherent in international relations and law on counterterrorism remain underdeveloped. In order to analyse the conflicting norms and values within the search for an international jurisdiction of global terrorism, this chapter evaluates the traditional systematic interpretation before making the case for a more nuanced understanding of the norm conflict in international counterterrorism jurisdiction.