For decades, the United Nations Security Council (UNSC) has been describing terrorism as a threat to peace. More than half a decade ago, it ‘created’ a tribunal to deal with terrorist crimes, the Special Tribunal for Lebanon (STL) 1. The fact that the UNSC itself gave birth to this tribunal is an extraordinary legal manifestation of the international criminal dimension of terrorism. Not surprisingly, the STL ruled that terrorism in time of peace is an international crime 2. However, the alleged failure of the “international community […] to agree on a generic definition of terrorism for the purposes of prohibition and/or criminalization” 3 continues to drive many scholars away from acknowledging that terrorism is a core crime side‑by‑side with genocide, aggression, crimes against humanity and war crimes. The main reason for this reluctance lies in the lack of a universal or quasi‑universal treaty containing a written and comprehensive definition of terrorism. This reluctance is unwarranted. It fails to fully grasp not only the significance of customary law but also that extant jus cogens law is not treaty law, but rather (non‑written) rules created by the international community of states as a whole. This universal law emerges through the normal customary process and, arguably, through binding resolutions of the representative of the international community on matters of war and peace, i.e. the UNSC.