Russia’s invasion of Ukraine in 2022 poses an extraordinary challenge to the post-World War II legal order, and more particularly, the prohibition on the use of force enshrined in Article 2(4) of the U.N. Charter. While international rules and institutions were unable to prevent the war, they have not failed to respond to it. Litigation has been brought before international and domestic courts and tribunals, and accountability mechanisms for the commission of atrocity crimes and the crime of aggression have been invoked and proposed. This panel will analyze whether the conflict and the international community's reaction to it create a risk of setback or have the potential to advance applicable principles and rules of international law