The article analyzes the Advisory Opinion of the International Court of Justice of the United Nations in 2019 “On the Legal Consequences of the separation of the Chagos Archipelago from Mauritius in 1965”. In this Conclusion, the International Court of Justice proceeds from the position that the subject of the right to self-determination of peoples is the entire population of some administrative-territorial unit, in this case the former British colony of Mauritius, in which included the Chagos Archipelago. Since, according to the International Court of Justice, this archipelago was unlawfully separated by the British colonial authorities from Mauritius, the decolonization of Mauritius has not been completed and the UK has the obligation to terminate its administration of the Chagos Archipelago and return it to Mauritius. At the same time, the evicted inhabitants of the Chagos archipelago still retain their right to self-determination, although in fact they have not lived in the archipelago for more than fifty years and are deprived of the opportunity to return there. The article draws attention to the fact that when deciding whether or not the inhabitants of the Mauritius and the Chagos archipelago are part of the same people exercising their right to self-determination, the International Court of Justice did not consider the existence of any linguistic, cultural, economic connection between them, an ethnic community. The International Court of Justice only established that both the Mauritius and the Chagos Archipelago became part of the same colonial possession of Great Britain and concluded that both the inhabitants of the Mauritius and the former inhabitants of the Chagos archipelago are a single subject of the right to self-determination. Also examines the attempts of forcibly evicted residents of the Chagos archipelago to defend their rights in both domestic and international courts. © Санкт-Петербургский государственный университет, 2025.