The crime of aggression amendment to the statute of the International Criminal Court (ICC) that was adopted in Kampala in 2010 was activated on 17 July 2018. This article argues that this new criminal provision is open enough to allow legally equally sound, but mutually exclusive, arguments that lead to opposite positions on whether the use of force in a particular situation is or is not a crime of aggression. It thereby enables the translation of political contestation on the causes of war and legitimacy of use of force into the moralized language of international criminal law, in the setting of a criminal court of law. This article shows how and why the crime of aggression norm is left open to allow contrary argumentation, in particular through its `manifest violation' criterion, how the openness of the norm is used in argumentation about the lawfulness/legitimacy as well as aggressiveness of Russia's role in separating Crimea from Ukraine as well as what it means to transpose political contestation into a criminal courtroom setting. The article forebodes that it puts the ICC in a Catch-22 position. Whether it allows the accused to argue its counter-narrative or not, it will be accused of holding a show trial when prosecuting for the crime of aggression. In a time when the ICC's legitimacy is under great stress, this article warns that if prosecutions for the crime of aggression will take place, they are more likely to leave behind the bad taste of a show trial than achieve much in terms of administering justice, suppressing aggression and contributing to more peaceful interaction between states.