The Use of Force and International Law

INTRODUCTION

The first Part of this book provides an examination of the contemporary prohibition of the threat or use of force, as found within Article 2(4) of the United Nations (UN) Charter and in customary international law. Not only is this a pivotal rule within the international legal framework governing the use of force, but is also a ‘cornerstone’ provision of the UN Charter and a norm of great importance within international law more generally. Nonetheless, it has given rise to some controversy in regard to both its breadth and scope of application and the specific meaning of ‘force’ leading to the observation that there is a ‘lack of agreed-upon definitions, criteria and thresholds for application’.

As such, the first of the chapters in this Part provides an exposition of the general breadth and scope of the contemporary prohibition, while the following chapter examines the specific meaning of ‘force’ that is the focus of it. Only by understanding this fundamental norm, including its difficulties, can one fully appreciate the actual and proclaimed exceptions to it that are addressed in the subsequent sections of the book. Together, the chapters provide an understanding of the design and function in practice of this fundamental norm of international law. Furthermore, an appreciation of the contours and application of these exceptions will provide a greater understanding of the circumstances in which we might be able to conclude that the prohibition has been breached.

The prohibition does not operate in an historical vacuum and, in understanding its breadth and scope, one must first understand where it is positioned along the historical continuum of efforts to regulate force. Section 1 of this chapter therefore sets the contemporary prohibition in this context. Section 2 then examines the sources of the prohibition, as found in Article 2(4) of the UN Charter and in customary international law, but also its status as a ‘peremptory’ or ‘jus cogens’ norm of international law and what this means in terms of the prospects for its adaptation and modification in the future.