From the vanishing point back to the core: The impact of the development of the cyber law of war on general international law

The law of war was famously described by Sir Hersch Lauterpacht as being ‘at the vanishing point of international law’. However, in a historical twist, international legal scrutiny of cyber operations emerged and developed precisely through the optics of the law of war. This paper analyses the influence that the development of the cyber law of war has had and might yet have on the ‘core’ of international law, in other words, on general international law. It analyses three key dimensions of the relationship between the law of war and general international law: systemic, conceptual, and teleological. It argues that, firstly, a systemic-level shift has taken place in the discourse, resulting in the academic debate and state focus moving from law-of-war questions to questions of general international law including sovereignty, non-intervention, and state responsibility. A better understanding of this trend should allay the fears of fragmentation of international law and inform the debate about the relationship between the law of war and ‘core’ international law. Secondly, this development has created fertile grounds for certain concepts to migrate from the law of war, where they had emerged, developed or consolidated, into general international law. A case in point is the functionality test, which originated as a compromise solution to determine whether a cyber operation amounts to an ‘attack’ under the law of war, but which may offer additional utility in other areas of international law including the law of state sovereignty and the law of arms control and disarmament. Thirdly, however, it is imperative that the unique teleological underpinning of the law of war is taken into consideration before introducing its rules and principles to different law. Secondly, this trend has allowed for specific concepts to migrate from the law of war where they had originated, evolved or consolidated and to influence other areas of international law. An illustrative example is the functionality test, which offers significant utility for the law of state sovereignty as well as the law of arms control and disarmament. Thirdly, however, it is imperative that the unique teleological underpinning of the law of war is taken into account before introducing its rules and principles to different normative contexts. Paradoxically, a blanket transplantation of these norms might in practice jeopardise the underlying humanitarian considerations.