Beyond the res judicata doctrine: The nomomechanics of ICJ interpretation judgments

Res judicata is a core belief of international law; the ICJ’s judgments are seen as final and without appeal, to doubt that is apparently equal to calling the entire international legal order into question. But the doctrine is not as absolute as the orthodoxy makes it out to be, neither as a matter of positive international law nor as a statement of legal theory. Even final judgements are not always final and appeals procedures and judicial review are not special in that they engage res judicata whereas regular legal change does not; rather, both do from a legal-theoretical vantage-point. This article makes the point by looking at ICJ interpretation judgments under Article 60; it argues that, far from leaving the original judgment’s res judicata intact, interpretation judgments actually impinge or even disrupt it. The article discusses ICJ interpretation judgments (the 2013 judgment in Preah Vihear serving as convenient example), introduces Adolf Julius Merkl’s Error Calculus theory as the theoretical framework best suited to analysing the nomomechanics and critiques the Preah Vihear interpretation judgment as change disguised as a hermeneutic exercise. It then turns the critical enterprise on its head to look at the Error Calculus theory itself to lay the groundwork for an even more audacious argument that the Error Calculus does not depend on errors in the narrow sense of the word: it is neither an ex post ratification of an imperfect norm nor a confirmation of invalidity, but the derogation of a perfectly valid norm.