This chapter argues that while many international law actors neglect their obligations to combat impunity and maintain international law and order, the European Union is a driving force in the fight against impunity for core international crimes (CIC) committed on the territory of Ukraine; it supports both national investigations in the EU States Parties and international criminal justice. The European Union played an important role in Ukraine’s ratification of the Rome Statute and supported the ICC in investigating international crimes committed in Ukraine after Russia’s full-scale invasion of Ukraine. Domestic investigations of core international crimes allegedly committed in Ukraine have been launched in at least 14 EU Member States and Eurojust’s coordination of national authorities allows for an effective fight against impunity. The raised issue is the fighting of impunity and future peace treaties with Russia and in any case the fight against impunity and justice should be served, and all those who committed international crimes to be held accountable.