Aggression has been a hot topic ever since it entered the realm of international criminal justice at the Nuremberg and Tokyo trials after the Second World War. It now belongs to the category of “the international core crimes”, together with war crimes, crimes against humanity and genocide. A – provisional – point of culmination in the legal status of aggression as an international crime is its inclusion in the list of crimes that come within the jurisdiction of the International Criminal Court.

Despite its status as the “supreme international crime”, suggesting that aggression is more serious than the other international crimes, aggression is not an uncontroversial crime. Ever since its appearance, there has been disagreement over its actual meaning. Unlike for war crimes and genocide, no specialised convention for aggression has been adopted after the Second World War. Whereas there seems to be a growing consensus that aggression is prohibited under customary international law, and while it is even an international crime giving rise to individual criminal responsibility, no generally accepted definition of aggression exists as yet.

Professor Kemp's book is the first comprehensive study of the subject with a focus on individual criminal responsibility. He starts by looking at aggression within the general framework of the collective security system of the United Nations set up after the Second World War, offering a detailed analysis of the various developments leading to the prohibition of the use of force in its normative and institutional perspective. Then follows an indepth study of various steps leading to the criminalisation of aggression, comprising the transition from a State responsibility-oriented approach towards a greater emphasis on individual criminal responsibility. Hardly any progress has been made after Nuremberg and Tokyo as far as individual criminal responsibility is concerned. While the 1974 General Assembly Resolution defining aggression has a clear focus on State Responsibility, projects oriented towards introducing individual criminal responsibility for this crime did not materialise. None of the International Law Commission's draft s defining aggression as an international crime made it into a treaty, and very little, if any, national legislation and jurisprudence exist on the “supreme international crime”.