There are two ways in which States can support this new system for the promotion of peace through criminal justice: by ratifying the Kampala amendments, and by implementing them.
Current and future States Parties to the Rome Statute should ratify the amendments to facilitate the activation of the Court’s jurisdiction over the crime of aggression. There is no reason to wait with ratification, in particular as domestic ratification procedures can be very lengthy. Every ratification sends a signal about the importance of the amendments to other States Parties and thus contributes to a global momentum to ratify. The ICC can only take up its functions with respect to the crime of aggression if States empower it to do so through at least 30 ratifications, and through a one-time activation decision in 2017.
All States, not just States Parties to the Rome Statute, should also consider including the definition of the crime of aggression in their domestic criminal codes, thereby empowering their own judiciary to help deter acts of aggression. Some two dozen States already had such criminal provisions prior to the Kampala Conference. Since then, some States have added such provisions in their criminal codes or aligned their domestic criminal codes with the internationally agreed and negotiated definition of aggression in the Rome Statute, and others are in the process of doing so.
Setting up domestic laws to help prevent the worst crime under international law should be a priority for all States that wish to promote the rule of law. Future acts of aggression must be deterred, and future perpetrators should not go unpunished due to missing or insufficient domestic legal standards. All leaders should have to consider the legality of their actions carefully before deciding to use force against another State.