Abstract Since the Kampala Amendments filled the placeholder in the Statute of the International Criminal Court (ICC) with a comprehensive definition of the crime of aggression, States Parties have felt encouraged to implement the so-called ‘crime of crimes’ into domestic law. This article gives an overview of how these early implementers defined the crime of aggression and designed provisions on domestic jurisdiction. The fast track approach to domestic implementation would have been to copy the definition contained in Article 8bis of the ICC Statute and extend the existing jurisdictional regime applicable to other international crimes. Instead, states often opted for a (slightly) modified definition and occasionally decided to deviate from the jurisdictional provisions applicable to other core crimes.