Unveiling the 'author' of international law — The 'legal effect' of ICJ's advisory opinions.

This article examines the legal authority and effects of advisory opinions issued by the International Court of Justice (ICJ), focusing on their non-binding nature and potential to produce authoritative legal determinations. Using the recent Mauritius/Maldives Judgment by the International Tribunal for the Law of the Sea (ITLOS) Special Chamber as a case study, it highlights how the Special Chamber treated the ICJ’s Chagos Advisory Opinion as an authoritative pronouncement that effectively resolved the sovereignty dispute over the Chagos Archipelago, despite the UK’s non-consent and continued claims. The article distinguishes between de jure authority (binding legal effect) and de facto authority (persuasive or authoritative influence) of ICJ advisory opinions, arguing that while these opinions lack formal binding force, they can carry definitive legal weight and function as “judicial givens” that other international bodies find difficult to contest. It further explores the implications of this approach for the Monetary Gold principle, international adjudication, and the legal policies of States and the ICJ itself, suggesting a shift toward recognizing advisory opinions as integral to the development and application of international law beyond their traditional advisory role.