Two Takes on Chagos: Reconciling the Advisory Opinion with the Res Judicata Effect of the UNCLOS Arbitral Award

Before the International Court of Justice (ICJ) issued its Advisory Opinion on the Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, an arbitral tribunal constituted under Annex VII of the United Nations Convention on the Law of the Sea (UNCLOS) had already ruled on closely related questions. Even though the UNCLOS tribunal had declined jurisdiction over the ‘sovereignty dispute’, the tribunal made several determinations of potential relevance to the proceedings before the ICJ, notably on the international legal status of the 1965 agreement between Mauritius and the UK.