Territories & dependencies of Mauritius
The Constitution of Mauritius provides that Mauritius includes the islands of Mauritius, Rodrigues, Agalega, Tromelin, Cargados Carajos and the Chagos Archipelago, including Diego Garcia and any other island comprised in the State of Mauritius. Mauritius has always maintained that it has sovereignty over the Chagos Archipelago but has not been able so far to exercise its sovereignty.

The total land area as per the Mauritian geography is 2040 km2 (excluding the Chagos Archipelago), making it the 181st largest nation in the world by size. Just off the Mauritian coast lie some 49 tiny uninhabited islands and islets (see Islets of Mauritius), some of them are used as natural reserves for the protection of endangered species. Mauritian territory also incorporates the island of Rodrigues, which is situated some 560 kilometers to the east and is 104 km2 in area. Two tiny dependencies, the Agalega Islands situated some 1,000 km to the north of Mauritius and the Cargados Carajos Shoals (also known as the St. Brandon Rocks) situated some 430 km to the north-east of Mauritius, both with total land area of 71.2 km2. The population estimate (as of 1 July 2011) for the whole republic is 1,286,340, of whom 633,916 were males and 652,424 females. For the island of Mauritius only it is 1,248,129 and Rodrigues island 37,922. Agalega and St. Brandon had an estimated population of 289. Mauritius and France both claim sovereignty over Tromelin, small islands that lie 430 km to the north-east of Mauritius.

The nation's exclusive economic zone (EEZ) is about 1.2 million square kilometers in the Indian Ocean. Four fishing banks fall within EEZ limits, the Soudan Banks (including East Soudan Bank), Nazareth Bank, Saya de Malha Bank, Hawkins Bank. In 2011 the United Nations endorsed the joint submission of Mauritius and Seychelles to extend their continental shelf of 396,000 km2 in the Mascarene region which gives the two countries sovereign right to jointly manage and exploit the seabed and subsoil of the joint area.

Mauritius sought to regain sovereignty, lost just before independence in 1968, over the Chagos Archipelago (1,931 kilometers to the northeast) which includes the Diego Garcia atoll, all of which comprise the British Indian Ocean Territory (BIOT). The Chagos has been part of Mauritius since the 18th century when the French first settled the islands. All of the islands forming part of the French colonial territory of Isle France (as Mauritius was then known) were ceded to the British in 1810 under the Act of Capitulation signed between the two countries. But when Mauritius became independent in 1968 the United Kingdom excised the Chagos Archipelago from Mauritius and leased Diego Garcia, the main island of the archipelago, to the United States under a 50-year lease (which expires in 2016 and comes up for renewal in 2014). After initially denying that the islands were inhabited, British officials forcibly expelled approximately 2,000 Chagossians who had lived on those islands for centuries to mainland Mauritius to allow the United States to establish a military base on Diego Garcia. Since 1971, only the atoll of Diego Garcia is inhabited only by some 3,000 UK and US military and civilian contracted personnel.

The detachment of the Chagos was a clear violation of international law. United Nations' resolutions banned the dismemberment of colonial territories before independence. Mauritius has repeatedly asserted that the British claim that the Chagos Archipelago is one of its territories is a violation of law and of UN resolutions. The UK has stated that it has no doubt about its sovereignty over the Chagos but has also said that the Chagos will be returned to Mauritius once the islands are no longer required for defense purposes. Given the absence of any progress with the UK, Mauritius has decided to "internationalize" the dispute and take up the matter at all appropriate legal and political forums. The African Union and the Non-Aligned Movement have expressed unanimous support for Mauritius on the Chagos issue.

Today the exiled Chagossians are still fighting to go back to their homeland, claiming that the forced expulsion and dispossession (see Depopulation of Diego Garcia) was illegal.

Marine protected area
The British Government established a marine protected area (MPA) around the Chagos Islands known as the Chagos Marine Protected Area which was created on the 1st April 2010 and enforced on the 1st November 2010. It is the world's largest fully protected reserve, twice the size of Great Britain. The designation proved controversial as the decision was announced during a period when the UK Parliament was in recess.

On December 1, 2010, WikiLeaks release a leaked US Embassy London diplomatic cable dating back to 2009 exposed British and US calculations in creating the marine nature reserve. The cable relays exchanges between US Political Counselor Richard Mills and British Director of the Foreign and Commonwealth Office Colin Roberts, in which Roberts "asserted that establishing a marine park would, in effect, put paid to resettlement claims of the archipelago’s former residents." Richard Mills concludes:

“ Establishing a marine reserve might, indeed, as the FCO's Roberts stated, be the most effective long-term way to prevent any of the Chagos Islands' former inhabitants or their descendants from resettling in the [British Indian Ocean Territory]. ”

The cable was classified as confidential and "no foreigners", and leaked as part of the Cablegate cache.

The Government of Mauritius initiated proceedings on 20 December 2010 against the UK Government under the United Nations Convention on the Law of the Sea (UNCLOS) to challenge the legality of the ‘marine protected area’. Mauritius considers that the UK, not being a “coastal State” under UNCLOS and international law, had no authority to purport to establish a marine protected area around the Chagos Archipelago and that the MPA was not compatible with the rights of the Chagossians.

The Mauritian Prime Minister Navinchandra Ramgoolam also stated that:

“ Only Mauritius can declare an exclusive economic zone on the Chagos Islands on the Clause 5 of the Convention of 1982. Since then, it is public knowledge that the true reason for the creation of the MPA, as revealed by Wikileaks was to prevent the Chagossians from returning to Chagos.