The concept of res judicata in international adjudication is not merely a technical procedural matter, but one that reflects deeper ideological and philosophical choices about the nature and purpose of the judicial process. Understanding res judicata broadly or narrowly points to different ideas of adjudication, different conceptions of legal reasoning, and different notions of constraint for the court, the parties, and third states. This chapter explores the challenges of applying the doctrine of res judicata in international adjudication, focusing on the temporal disconnect between the original decision and subsequent proceedings aimed at enforcing or interpreting that decision. The finality imposed by res judicata creates a need for the second adjudicator to reconstruct the precise contours of the original findings, a process inherently influenced by the present context, perspectives, and ideology of the decision-maker. In particular, the chapter focuses on the scope of res judicata, discussing the implications of narrow and broad understandings of the principle, and the difficulty in determining what has actually been decided in a previous judgment. The recent case of Guyana v. Venezuela before the International Court of Justice (ICJ) is used as a case study to illustrate these challenges, with the court ultimately re-characterizing the Monetary Gold principle to avoid the preclusive effect of its earlier decision. The essay proposes a solution based on a broader notion of preclusion, drawing inspiration from Italian procedural law and Roman law concepts of litis contestatio and res in judicium deducta. This approach would incentivize parties to put forward all arguments at the outset and reduce the risk of piecemeal or inconsistent judgments. Even so, this expansive notion of preclusion reflects a particular ideological choice, prioritizing stability and the protection of rights granted in the first judgment over other interests, such as those of third parties.