State parties to the International Criminal Court made history in 1998 when they agreed to include the crime of aggression as one of four crimes within the jurisdiction of the Court. The crime, however, was left undefined in 1998, and the Court’s jurisdiction over the crime of aggression has been postponed until state parties can agree to a definition at a Review Conference in 2009. Reaching such an agreement would represent the first time in history that national leaders would be bound by a specifically defined crime of international aggression with sanctions wielded by an international court. Parties to the Court, however, differ widely over two questions: whether the crime should be defined narrowly or broadly, and who should decide when aggression has occurred, thus triggering the Court’s jurisdiction over the culpable individuals. The two questions have largely split state parties between those citing the demands of the current international system and those committed to basic principles of fairness. This Note suggests that by applying the traditional utilitarian and retributivist rationales for the criminal law, state parties may be able to reach the most balanced and principled definition of aggression.