Crime of Aggression against Ukraine The Role of Regional Customary Law

In the discourse around prosecution of perpetrators of the crime of aggression against Ukraine, there is a need to consider the impact of Eastern European regional norms, both treaty-based and customary. This concerns both the interpretation of principles of responsibility for the crime of aggression as well as the modes of prosecution thereof. The article argues that, in Eastern Europe, the crime of aggression is a well-established norm of international and national law, and aggression - as a conduct by a state - is defined based on the principle of first use of force, while political, economic and any other justifications in order to avoid responsibility are disallowed. Individual responsibility for the crime of aggression represents a departure from the International Criminal Court's Rome Statute standard and is instead based on the International Military Tribunal's Charter, which limits its scope to responsibility for a war of aggression. At the same time, it does not preclude, for example, prosecution of those responsible for the administration of occupied territories. As a consequence, the leadership clause might be understood as broader in comparison to the Rome Statute standards.