The purpose of the course is to examine the far-reaching changes that have occurred since the nineteenth century to the body of law governing recourse to the use of force (jus ad bellum). In 1945 the United Nations Charter prohibited States from resolving their international disputes by the threat or use of force except, subject to certain conditions, in self-defence, and established a system of collective security whereby the Security Council would take action in the name of the international community to maintain or restore international peace and security.

The Cold War obstructed the effective realisation of these provisions. As a result of Security Council paralysis and in order to protect perceived essential national interests, some States adopted expansive concepts of self-defence or other justifications for recourse to force of doubtful legality.

The collapse of the Soviet Union in the early 1990s led to a renewal of hopes that a system of collective security might function as originally intended. Those hopes have not been entirely fulfilled, but the concept of international peace and security has been expanded in the last few decades to embrace violations of human rights, denial of democracy, and urgent humanitarian needs, thus justifying collective action under Security Council mandates.

The course will not revisit in any great detail the normative content of self-defence, both individual and collective (in this regard students are encouraged to revise their LAWS8183 Advanced Principles of International Law materials), but will examine other contentious or sometimes overlooked issues: such as implied authorisations and intervention by invitation. More traditional topics, such as the doctrine of humanitarian intervention and the idea of a responsibility to protect (R2P) will also be considered.

Topics may include:

• The history of the jus ad bellum: from the "Just War" theory to the United Nations Charter;
• The scope of the prohibition: can it cover cybercrime? What is a threat? Who are the addressees of the prohibition?
• Military intervention by invitation;
• Chapter VII of the United Nations Charter and so called implied 'authorisations' to use force;
• The role of regional arrangements in the use of force;
• Humanitarian intervention and the 'Responsibility to Protect'.