Despite the fundamental importance of the prohibition of the use of force between States in the international legal order, there remains genuine uncertainty amongst States, scholars and jurists about what this term means. This forthcoming monograph with Cambridge University Press addresses this question and defines a prohibited “use of force” between States under article 2(4) of the UN Charter. It is adapted from my PhD dissertation, which was prepared under the supervision of Professor Claus Kreß and awarded the grade summa cum laude.
The book is divided into three parts and nine chapters. Part I deals with the sources of the prohibition of the use of force between States under international law. Since the prohibition of the use of force is found in both treaty (the UN Charter) and customary international law, this part is concerned with whether its content is identical under both sources and which one to interpret or apply. It argues that the customary rule emerged as a result of article 2(4) and that due to the relationship between the two sources, we should focus on interpreting the UN Charter to determine the meaning of a prohibited “use of force” under international law. Part II proceeds to apply treaty interpretation to article 2(4) of the UN Charter, looking at all of the terms of that provision. In particular, it focuses on the meaning of “international relations” and especially, “use of force”. In doing so, it identifies the elements of a “use of force”, namely, the required means, effects, gravity and intention. Part III then challenges the previously accepted paradigm of a “use of force” as a coherent concept by pointing out anomalous State practice in this field. It then proposes an original framework for defining an unlawful “use of force” under article 2(4), bringing together each of the elements of that provision. In contrast to the prevailing view, I argue that none of the elements of a “use of force” – including physical means or physical effects – is strictly necessary for the definition to be met. Rather, I propose that a “use of force” is a “type”, meaning that its elements must be weighed and balanced to reach a certain threshold, which may differ depending on the type of force used and the domain in which it takes place.