Is self-defence against a cyber attack permitted? What about a cyber counter-attack against a conventional or cyber attack? Under Article 51 UN Charter self-defence is permitted ‘if an armed attack occurs’. Many scholars agree that a cyber attack amounts to an ‘armed attack’ when it causes harm or damage approximately comparable to a ‘kinetic’ or conventional attack and in particular when it hits ‘critical infrastructures’. Also in cyberspace, when permitted, individual or collective self-de¬fence has to meet the requirements of necessity, proportionality and immediacy. Two further major problems linked with self-defence against cyber attacks discussed in this chapter relate to the permissibility of anticipatory self-defence and self-defence against non-state actors or against the breach by a state of its duty of prevention of cross-border harmful private acts. The chapter concludes with some scepticism about the ‘use of force’ and analogy-based approaches in the literature suggesting that the law enforcement paradigm and non-forcible responses are preferable to the escalating militarization of cyberspace and noting that even when self-defence is permitted in cyberspace the necessity requirement demands of states to abide by a continuing obligation to implement passive and active electronic defences. In any case the prevailing approach serves, in addition to trying to identify reasonable rules, a twofold purpose, that is, deterring possible attacks and promoting the rules which could possibly govern major cyber attacks at the moment when they occur so as to have at that very moment the international community ‘prepared’ to share the view that the attack is indeed ‘equivalent’ to a kinetic attack which justifies a kinetic response.
This chapter examines the main developments occurred in international law since the beginning of the 20th century. It will take into account the main areas of international law (i.e. international humanitarian law, international organizations, territorial sovereignty and domestic jurisdiction, minorities, human rights, the environment and sustainable development, international terrorism, international criminal law and justice, foreign investment, international trade and finance, self-determination of peoples, the use of force and measures short of war, and international adjudication), as well as the most internationally relevant historical events and related theoretical issues, in four periods: the years up to the end of World War I (1899-1918), the Interwar Period and World War II (1919-1945), the Cold War Period (1945-1989) and the Post-Cold War Period (1989-present). It will conclude by emphasizing how current trends towards souveranism in many areas of the world, together with the neoliberalization and AI-driven global automation of all human expressions, going well beyond the economic sphere, are seriously undermining the achievements of the internationalism and humanitarianism of the past.