Balancing Procedural and Substantive Rules in light of the Relationship between Immunity and Responsibility in the Case Law of the ICJ

The immunity of the state has a strong basis in customary international law. But the nature of these rules is not exactly obvious. Lawyers have different points of view on determining immunity as procedural or substantive rule. Twice the International Court of Justice had the chance to evaluate the nature of state immunity and its probable conflict with substantive rules. The first time, in the case concerning Yerodia arrest warrant (Congo v. Belgium) in 2002 and the second time, in the case concerning the Jurisdictional Immunities of the State (Germany v. Italy: Greece intervening) in 2012. The question of this paper is whether the distinction between the procedural rule of immunity and a substantive jus cogens rule as is used by ICJ has a legal basis or can it be legally challenged? It will be argued that the ICJ approach in using the distinction can cause problems like descending the position of jus cogens and impunity for the perpetrators of the most serious crimes. Thus, the ICJ should be more cautious in using such a reasoning.