International Law

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In the Matter of the Chagos Marine Protected Area Arbitration

(Mauritius v. UK), Award, 18 March 2015

On 1 April 2010, the UK declared the world’s largest Marine Protected Area (MPA) around the Chagos Archipelago. The Archipelago is one of 14 remaining British overseas territories, administered by the UK as the British Indian Ocean Territory (BIOT). In contrast to other British overseas territories such as the Falklands/Malvinas and Gibraltar, BIOT is not on the UN list of non-self-governing territories. There is currently no permanent local population because the UK cleared the archipelago of the Chagossians between 1968 and 1973.

Mauritius and the UK both claim sovereignty over the Chagos Archipelago. The largest island of the Chagos Archipelago – Diego Garcia – has since the late 1960s housed the most important US military base in the Indian Ocean. The UK leased the island for defense purposes to the US in 1966, prior to Mauritian independence in 1968.

In the Matter of the Chagos Marine Protected Area Arbitration (Mauritius v. UK), an international arbitral tribunal issued its award on 18 March 2015. The tribunal found that the UK’s declaration of the MPA disregarded Mauritius’ rights, rendering the MPA unlawful. The award implies that the UK must meaningfully consult Mauritius regarding anything that significantly affects the Archipelago, such as the renewal of the lease for Diego Garcia.
Among others, Mauritius submitted to the tribunal:
• That the UK was not entitled to declare a marine protected area because it was not a coastal state under UNCLOS (the ‘sovereignty claim’, according to the UK)
• That the UK’s unilateral declaration of the MPA was incompatible with the UK’s substantive and procedural obligations under UNCLOS

Learning Objectives

• To get of the sense of the types of issues that international law is concerned with, such as sovereignty over territory, environmental protection and the safeguarding of human rights
• To appreciate the role that international dispute settlement may play in resolving or mitigating disputes between states
• To learn how history and politics influence disputes between states
• To appreciate the interaction between international and UK domestic constitutional law in the form of the Lancaster House Undertakings
• To learn how the principle of estoppel operates in international law