INTRODUCTION

This chapter charts the historical development of the criminalisation of aggression as a crime under international law. It also traces the development in international criminal law towards the acceptance of individual (as opposed to state) criminal liability for aggression.

In the previous chapters it was explained how the use of force by states became outlawed. The use of force is no longer acceptable as an instrument of foreign policy. The jus ad bellum became the jus contra bellum.

The liberal ideal of collective security manifested in the twin reactions to the use of force by states: The essentially political response, where the Security Council of the UN determines when a situation is regarded as a threat to or breach of peace, or an act of aggression; and the legal response where the International Court of Justice (ICJ) has a prominent role to play to determine whether the use of force violates the relevant provisions of the UN Charter, notably the prohibition of the use of force provided for in Article 2(4). The Security Council, which is the most important body to maintain international peace and security under the UN-dominated collective security system, may also create international criminal tribunals as a response to threats to peace and security, as it did in reaction to the conflict in the Former Yugoslavia in the early 1990s and with the genocide in Rwanda in 1994. Thus it can be said that the Security Council has set precedents in terms of Chapter VII of the UN Charter whereby international peace and security can be maintained by various methods like the use of armed force (for example during the Korea conflict in the 1950s), economic sanctions (for instance against apartheid South Africa), and also the creation of international criminal tribunals to try individuals responsible for serious crimes under international law (the aforementioned creation of the ad hoc tribunals for Rwanda and the former Yugoslavia).

The shift from jus ad bellum to jus contra bellum has been an important historical development in international law. Another important development in international law has been the acceptance of individual criminal liability for certain serious crimes under international law.