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.

Is a Dutch court able to vary the terms of an English trust by applying English trust law if a Dutch court does not normally have such a wide discretionary power? Is a Dutch court able to apply a rule from Moroccan family law that designates the court itself as custodian if Dutch law does not confer such a task on a court? Is a Dutch court able, when it is asked to pronounce a divorce on the basis of Jewish law, to act in a religious capacity? These questions show possible limits of the judicial function in private international law matters. Private international law doctrine knows several theories that are intended to provide guidelines for answering these questions. After having explored those theories, the author concludes that at least three limits of the judicial function can be distinguished. If a Dutch court concludes that in applying the foreign law that has been designated by the Dutch conflict rules it would encounter one of these limits, then the court is not competent from a constitutional point of view to apply that foreign law, in conformity with the purpose intended by the foreign legislature. However, this does not mean that the court has no competence to give a decision at all. The author stresses that it is desirable, and sometimes even compulsory, that the court looks for an alternative decision to prevent parties from being sent home ‘empty-handed’.

The ICJ in its judgments on the preliminary objections in the Legality of Use of Force cases held that it had no jurisdiction to hear the claims. Despite the unanimous concurrence in that result, it is clear that there were deep divisions within the Court as to the ground on which that decision should have been reached; only a bare majority subscribed to the reasoning that the Court was required to rule on the question of its jurisdiction ratione personae in relation to Serbia and Montenegro's uncertain status within the United Nations prior to 2000. The minority judges were highly critical of the choice of that basis of decision, in particular given its apparent implications for other cases pending before the Court.