27 he use of force is undoubtedly among the most debated topics within international law as well as international relations. Indeed, the rules concerning the use of force form a central part of the international legal system, and, together with other fundamental principles, they have for a long time provided the framework for organised international intercourse and successful co- existence of states. The circumstances in which the use of force might be justified concerned already the earliest legal writers, for example, Aristotle and Cicero, and the topic has remained at the centre of The Use of Force in the Modern World: Recent Developments and Legal Regulation of the Use of Force By René Värk* political and legal debates since those early times. Both domestic societies and the international community need to limit and regulate the use of force in order to secure peaceful, harmonious and mutually beneficial co-existence of individuals or states within the respective societies or the international community. The domestic legal systems have generally managed to monopolise the use of force in favour of the governmental institutions, which means that people have given up their right to use force, save for self-defence, in return of the guarantee that the mentioned institutions will instead protect their person and property. The international legal system has attempted to move in the same direction since the end of the First World War, but, due to its characteristic features, the task has proved quite difficult. This is so, because the international legal system lacks an effective enforcement mechanism, which can ensure the observance of international law if necessary. Unlike a domestic legal system, which can utilise different law enforcement authorities, the international legal system has to rely simply on such means as consent, good faith and reciprocity. Moreover, states do not only * René Värk is a Director for Academic Affairs and Lecturer in International Law, Institute of Law, University of Tartu.