This article considers the approach to the res judicata principle taken by the International Court of Justice (ICJ or the Court) and, specifically, its application in its 2016 judgment on preliminary objections in the latest dispute between Nicaragua and Colombia. The judgment joins the small number of ICJ decisions in which the Court was evenly split, an altogether rare situation, which, at the time of the decision, had not occurred since the Nuclear Weapons Advisory Opinion. Intriguingly, such a fracture seems to have been prompted by differences over the operation of a procedural principle the understanding of which is comparatively uncontroversial. Upon closer analysis, however, the disagreement reveals that more significant questions were at stake, with members of the minority issuing a vocal joint dissent and several individual declarations. This study will move in three parts: first, it will provide an overview of the nature and purpose of the principle of res judicata, its application in international adjudication, and its use by the ICJ; second, it will analyze the Court's reading of the principle in the case at issue; third, it will expose the broader implications of one such approach for the role and authority of the World Court and the international judiciary.