Res judicata (Latin: "a matter judged") is a foundational principle of both domestic and international law. It bars parties from reopening disputes that have already been settled by a final judgment of a competent tribunal, on the rationale that litigation must, at some point, end (interest reipublicae ut sit finis litium). The doctrine protects judicial economy, prevents inconsistent rulings, and shields parties from repeated harassment over the same claim.
In international law, res judicata is generally recognized as a "general principle of law" within the meaning of Article 38(1)(c) of the Statute of the International Court of Justice. Article 59 of the ICJ Statute reflects the principle by providing that decisions of the Court have no binding force except between the parties and in respect of that particular case, while Article 60 declares ICJ judgments final and without appeal.
Three elements are typically required for the doctrine to apply, often summarised as the triple identity test:
- Identity of parties (persona)
- Identity of subject matter or object (petitum)
- Identity of legal grounds or cause (causa petendi)
The ICJ confirmed and applied the doctrine in the Bosnia Genocide case (Bosnia and Herzegovina v. Serbia and Montenegro), Judgment of 26 February 2007, holding that its 1996 judgment on preliminary objections was res judicata and could not be reopened. Investment arbitration tribunals under ICSID have also wrestled with the doctrine, particularly in parallel proceedings.
Res judicata is distinct from related concepts. Stare decisis, the common-law doctrine of precedent, binds future cases generally, whereas res judicata binds only the specific parties to the prior dispute. It also differs from lis pendens, which addresses parallel ongoing proceedings rather than concluded ones.
For MUN delegates and IR researchers, the doctrine matters whenever questions arise about reopening ICJ judgments, challenging arbitral awards, or invoking prior rulings in committees referencing past UN or regional court decisions.
Example
In its 2007 *Bosnia v. Serbia* genocide judgment, the ICJ held that its 1996 ruling on jurisdiction was res judicata and refused to reconsider whether the Court had jurisdiction under the Genocide Convention.
Frequently asked questions
Generally no. Advisory opinions are not binding judgments between parties, so the formal doctrine does not attach, though their reasoning carries significant persuasive weight.
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