The crime of aggression requires that the perpetrator be in a position effectively to exercise control over—or to direct—the political or military action of a state. This requirement, called the “leadership clause,” has led to the view that private individuals are excluded from criminal responsibility because they lack the necessary authority over the state policy. In this Essay, I argue against this dominant view and outline an analytical framework for criminal complicity in a war of aggression.

This thesis examines the attribution of criminal responsibility for the crime of aggression in international criminal law. Prosecuting aggression is predicated by the so-called leadership clause—an individual can be held responsible only if he or she meets the requirement of being in a position of control over or to direct state action. This ‘control or direct’ clause—which replaced the ‘shape or influence’ standard that was applied in Nuremberg—is based on a simple normative premise: individual responsibility ought to be restricted to state leaders and exclude followers. This work argues that the notion of leadership in this context denotes a normative determination that the individual had a decisive influence over the state policy on using armed force. To make such a normative determination, the inquiry needs to include the power dynamics of the given state so as to properly comprehend which structures of power govern state policies. This argument is built on the basis of the conceptual structure of the definition of the crime of aggression and an analysis of relevant case law and international documents. To this end, the thesis constructs a conceptual framework that provides for general conditions for criminal responsibility based on the material (actus reus) and mental (mens rea) elements of the crime of aggression. Against this background, the work critically appraises perpetration and complicity and concludes that individual conduct that, at the very least, significantly affects the state act of the use of armed force is the kind of behaviour prohibited by the crime of aggression.

To adjudicate a claim on individual criminal responsibility, the court has to establish objective and subjective links between the individual and the crime. This article studies the material (actus reus/objective) elements of the crime of aggression (conduct, consequence and circumstance) and suggests a reading that solves most of the conceptual and practical issues regarding criminal responsibility for this crime. The main contribution is an ontological distinction between the material act of use of violence and the act of aggression, which are both subsumed under the term ‘state/collective act’. The former is a consequence element and therefore is to be understood in its naturalistic meaning – a perceivable result of one’s action. The latter is a legal-evaluative notion and as such constitutes a circumstance that renders the violation of the prohibitory norm (the union of conduct and consequence) as being wrongful. This distinction is crucial for the system of attribution of criminal responsibility, as different mental (subjective) elements apply to consequences and circumstances.