The International Court of Justice (ICJ) and the International Criminal Court (ICC) constitute two prominent international courts. However, there exists considerable variation in states' support for these two institutions. The Rome Statute, which recognizes the jurisdiction of the ICC has been ratified by over half the states in the world, only a third of states accept the compulsory jurisdiction of the ICJ. How are we to understand this variation in state support for these two courts? I argue that there is an inherent link between the quality of a state's domestic legal system (rule of law) and perceived legitimacy of an international court. Empirical analyses of states' support for the ICJ and the ICC show that rule-of-law states lend support to the ICC, a court perceived by the international community as legitimate. Alleged bias of the ICJ has, on the other hand, substantially weakened support for this court among rule-of-law states.