Since the creation of the British Indian Ocean Territory, a remnant of the British Empire has been subject of international legal dispute. The two most prominent are the request for an advisory opinion – currently under deliberation of the International Court of Justice (ICJ) – and secondly the arbitral proceedings under the Law of the Sea Convention (UNCLOS).

It all started when the United Kingdom separated the group of island of the Chagos Archipelago from its colony Mauritius in 1965. The Chagos Archipelago became part of the newly formed British Indian Ocean Territory. With the formal independence of Mauritius in 1968, the Chagos Islands remained part of the British Indian Ocean Territory. In 1971, the main island of the archipelago, Diego Garcia, was leased to the United States for the establishment of a military base. Consequently, the local Chagossian population of about 2.000 people was forced to move from the island and resettle on Mauritius. The Chagossians and their descendants claim the right to return. Both the United Kingdom and Mauritius claim sovereignty over the Chagos Islands.

Advisory Opinion ICJ

On 22 June 2017 the General Assembly of the United Nations adopted a resolution in which it decided to request an advisory opinion to the International Court of Justice (ICJ) titled: Request for an advisory opinion of the International Court of Justice on the legal  consequences  of  the  separation  of  the  Chagos  Archipelago  from  Mauritius in  1965”.

The request from the General Assembly is twofold: (a) was the process of decolonization of Mauritius lawfully completed when Mauritius was granted independence in 1968, following the separation of the Chagos Archipelago from Mauritius and having regard to international law? And (b) what are the consequences under international law, arising from the continued administration by the United Kingdom of the Chagos Archipelago, including with respect to the inability of Mauritius to implement a programme for the resettlement on the Chagos Archipelago of its nationals, in particular those of Chagossian origin?”

The two main issues concerning the Chagos Islands, namely the question of sovereignty and decolonization on the one hand and the legal consequences for the resettlement of the Chagossians, are now under deliberation of the ICJ. Last September hearings were held before the ICJ.

UNCLOS Tribunal

In 2010 a Marine Protected Area was created by the United Kingdom in the British Indian Ocean Territory. Comprising over 640,000 square kilometers, this marine protected area is one of the largest protected areas in the world, but it also makes it effectively impossible for resettlement of the Chagossians and their descendants. The creation of the Marine Protected Area was the cause for Mauritius to submit a claim to a tribunal established under Annex VII of the UN Convention on the Law of the Sea. On 18 March 2015 the tribunal issued an award in the case in which it rendered the Marine Protected Area not in accordance with the provisions of UNCLOS.

Academic legal research

These issues and certain domestic proceedings in the United Kingdom relating to the legal status of the Chagossian people, have been the subject of legal academic research and subsequent publications. A recent addition is titled: Fifty years of the British Indian Ocean territory: legal perspectives. This book, produced in response to the 50th anniversary of the British Indian Ocean Territory’s founding, also assesses the impact of the decisions taken in respect of the Territory against a wider background of decolonization while addressing important questions about the lawfulness of maintaining Overseas Territories in the post-colonial era.

See a selection of publications from our Catalogue below.

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Librarian's choice

A selection of relevant publications from the Peace Palace Library collection

Electronic publications

Aksensova, M. and Burke, C., "The Chagos Islands Award: Exploring the Renewed Role of the Law of the Sea in the Post-Colonial Context", Wisconsin international law journal, 35 (2017), No. 1, pp. 1-38.

Law, M., ‘The Chagos Request: Does It Herald a Rejuvenation of the International Court of Justice's Advisory Function’ Queen Mary law journal, 9 (2018) No. 1, pp. 25-48.

Murray, C.R.G. and Frost, T., The Chagossians' struggle and the last bastions of imperial constitutionalism, Rochester, Social Science Research Network, 2018.

Vine, D., Harvey, P. and Sokolowski, S.W., "Compensating a People for the Loss of Their Homeland: Diego Garcia, the Chagossians, and the Human Rights Standards Damages Model", Northwestern University journal of international human rights, 11 (2012), No. 1, pp. 149-182.


Allen, S. and Monaghan, C., Fifty years of the British Indian Ocean territory: legal perspectives, Cham, Springer International Publishing, 2018.

Allen, S., The Chagos Islanders and international law, Oxford, Hart Publishing, 2014.

Evers, S.J.T.M., and M. Kooy, Eviction from the Chagos Islands: displacement and struggle for identity against two world powers, Leiden, Brill, 2011.

Jeffery, L., Chagos islanders in Mauritius and the UK: forced displacement and onward migration, Manchester [etc.], Manchester University Press, 2011.

Ollivry, T., Diego Garcia: enjeux stratégiques, diplomatiques et humanitaires, Paris, L'Harmattan, 2008.

Sand, P.H., Atoll Diego Garcia: Naturschutz zwischen Menschenrecht und Machtpolitik, München, Utz, 2011.

Sand, P.H., United States and Britain in Diego Garcia: the Future of a controversial Base, New York, Palgrave Macmillan, 2009.


Allen, S., "Responsibility and Redress: the Chagossian Litigation in the English Courts", in Evers, S.J. and Kooy, M. (eds.), Eviction from the Chagos Islands: displacement and struggle for identity against two world powers, Leiden [etc.], Brill, 2011, pp. 127-152.

Kattan, V., "Self-Determination during the Cold War: UN General Assembly Resolution 1514 (1960), the Prohibition of Partition, and the Establishment of the British Indian Ocean Territory (1965)", Max Planck yearbook of United Nations law, 19 (2015) pp. 419-468.

Parlett, K., "Beyond the Four Corners of the Convention: Expanding the Scope of Jurisdiction of Law of the Sea Tribunals", Ocean development and international law: the journal of marine affairs, 48 (2017), No. 3-4, pp. 284-299.

Monaghan, C., "The Chagossians go to Strasbourg: Convention Rights and the Chagos islands: "Chagos Islanders v United Kingdom"", European human rights law review (2013), No. 3, pp. 314-325.

Sharpe, J.K., "Introductory Note to the Arbitral Tribunal Constituted under Annex VII of the 1982 United nations Convention on the Law of the sea ; Republic of Mauritius v. United kingdom & northern Ireland, Reasoned Decision on Challenge", International legal materials: current documents, 51 (2012), No. 2, pp. 350-381.

Talmon, S., "The Chagos Marine Protected Area Arbitration: Expansion of the Jurisdiction of Unclos Part XV Courts and Tribunals", The international and comparative law quarterly, 65 (2016), No. 4, pp. 927-951.

Zou, K. and Ye, Q., "Interpretation and Application of Article 298 of the Law of the Sea Convention in Recent Annex VII Arbitrations: An Appraisal", Ocean development and international law: the journal of marine affairs, 48 (2017), No. 3-4, pp. 331-344.


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