Why to implement the crime of aggression in domestic law
The ICC’s jurisdiction over the crime of aggression helps deter the illegal use of force, and to bring to justice those leaders that blatantly violate the prohibition of the use of force. That effect is even greater if the definition of aggression is implemented at the national level, as domestic courts do not encounter the same jurisdictional restrictions as the ICC. Most importantly, domestic rules criminalizing aggression could help prevent the leaders of that same country from committing aggression in the future. These leaders would, when taking decisions regarding the use of force, take such laws into consideration. Implementation thus serves the purpose of deterrence and emphatically signals to a domestic audience the illegality of aggression.
Already prior to the Kampala Conference, some 25 States had domestic provisions criminalizing aggression. These include Armenia, Azerbaijan, Belarus, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Estonia, Germany, Georgia, Hungary, Kazakhstan, Kosovo, Latvia, Macedonia, Moldova, Mongolia, Montenegro, Poland, Russian Federation, Serbia, Slovakia, Slovenia, Tajikistan, Ukraine, Uzbekistan. Some of them have since adapted their domestic legislation to align it with the Kampala definition, and some are in the process of doing so.
There is no legal obligation to implement the amendments on the crime of aggression originating from the Rome Statute, even though the Statute’s preamble recalls “that it is the duty of every State to exercise its criminal jurisdiction over those responsible for international crimes”.
Another consideration in this regard is the principle of complementarity, which also applies to the crime of aggression. A State Party that does not implement the definition essentially waives its primary right to deal with aggression cases within its own jurisdiction in the future and expresses a preference for international prosecution of such cases. This may not be in the interest of that State, as it may prefer to take it upon itself to prosecute its own nationals for having committed a crime of aggression rather than leaving the matter to the Court.
How to implement the crime of aggression in domestic law
Implementing the Rome Statute’s provisions on the crime of aggression in domestic law has two aspects: cooperation with the Court, and incorporation of the crime of aggression in the domestic criminal code.
Cooperation with the Court regarding investigations and prosecutions
The Rome Statute obliges all States Parties to cooperate with the Court and to adopt domestic laws that enable such cooperation. The need for such cooperation will in the future also arise with regard to the crime of aggression, once the jurisdiction is activated. Article 86 of the Rome Statute requires all States Parties to cooperate fully with the Court in its investigation and prosecution “of crimes within the jurisdiction of the Court”. This obligation is not limited to States Parties that ratify the amendments. All States Parties should therefore ensure that their domestic laws allow for such cooperation by the time the Court’s jurisdiction over the crime of aggression is activated.
Incorporation of the crime of aggression in the criminal code
While some 25 States already had domestic criminal provisions on the crime of aggression, many others did not, owing not least to the fact that until June 2010, there was no treaty-based and detailed international definition of the crime of aggression. When considering ratification of the Kampala amendments, many States will wish to reconsider their domestic criminal laws in this regard. Generally speaking, the safest way to implement the definition is to stick as closely as possible to the wording of Article 8 bis, and to focus domestic jurisdiction on crimes of aggression that might be committed by a State’s own leaders. It is reasonable to expect that the domestic criminalization of aggression will have the strongest deterrent effect vis à vis a domestic audience. Nevertheless, some States also extend their jurisdictional reach over acts of aggression committed by foreign leaders (on the basis of the principle of territoriality, or on the basis of universal jurisdiction). Such an extensive domestic criminalization of aggression raises a number of legal issues that are addressed in more detail in our Kampala Handbook.