International Counterterrorism Law is the first book to consider national terrorism legislation in every one of the 197 States worldwide. It explains how international counterterrorism law has become a distinct branch of international law, and what the different components are in both peacetime and armed conflict. The relevance and contribution of international humanitarian law, international criminal law, national criminal law, and international human rights law are examined in combination with global sectoral terrorism treaties and regional instruments to provide a thorough yet manageable account of the law's application. Real-life examples are used to inform the material, from Ukraine to Syria, to Iran and the unlawful actions of the Global War on Terror, so that the reader can understand how domestic and international terrorism has historically been treated by prosecutors and the courts.