Chapter 6 provides an overview of the general aspects of the right of self-defence. It first examines the concept of an ‘armed attack’ as found in Article 51, with the aim of shedding some light on the difficult issues and questions raised by this prerequisite for the invocation of the right of self-defence. It then goes on to provide an examination of the twin customary principles of necessity and proportionality, including a specific look at the controversial concept of armed reprisals, before moving on to examining military action for the protection of nationals who are located abroad. The right of self-defence exists in both individual and collective forms, and the chapter takes a specific look at the right of collective self-defence. Finally, it examines the role of the UN Security Council in the invocation and implementation of the right of self-defence, an aspect of the right which is prominent throughout Article 51.

The chapter examines the ICJ’s contribution to the law on the use of force. The author considers the Court’s case law on the prohibition of the use of force and its potential exceptions, most notably the law on individual and collective self-defence. He identifies the main conceptualisations, inconsistencies, disagreements, and limitations of the Court’s opinions, arguing that although the Court initially had a significant influence, it has faded significantly over the years as a result of what appears to be a conscious or strategic decision of its judges.