- Paola Gaeta, Paola GaetaProfessor of International Law, The Graduate Institute, Geneva
- Jorge E. ViñualesJorge E. ViñualesHarold Samuel Professor of Law and Environmental Policy, University of Cambridge
- and Salvatore ZappalàSalvatore ZappalàProfessor of International Law, University of Catania
This chapter analyses the enforcement of international law by States acting individually, that is, decentralized enforcement, including by their courts, as well as through retortion or countermeasures (once called reprisals). This is the typical form of enforcement under traditional international law. At the same time, enforcement might take place through measures taken by States acting collectively, that is, through mechanisms that include resort to collective measures, such as those adopted at the UN level (or within other international organizations), which can lead to collective sanctions. The first form of enforcement looks at the traditional law governing retortion and reprisals or countermeasures (as they are now called), as well as at the post-1945 law, taking into account that the ban on the use of armed force in international relations imposes that all enforcement measures taken by States individually must be peaceful. The second form examines the issue of collective sanctions, such as those taken at UN level.