The Chagos Island disputed started in 1965, when prior to Mauritian independence, the UK split the archipelago from the territory of Mauritius to form the British Indian Ocean Territory. The Republic of Mauritius has since then claimed that the UK’s dominance over the archipelago is a violation of UN resolutions, however until recently the UK had claimed its sovereignty motivated by military purposes. The area has been logistically strategic for the United States, especially the Diego Garcia island, from which 1800 inhabitants had been displaced and have not been permitted to return. The archipelago is renowned for its biodiversity and in 2010 the UK government declared the creation of a Marine Protected Area where fishing and extractive activities are prohibited.
On 22 May 2019, the United Nations General Assembly (UNGA) voted in favor of setting a six-month deadline for the United Kingdom to withdraw from the Chagos Archipelago, which would then be reunified with Mauritius. The vote took place after the ICJ in Den Haag released an advisory opinion stating: “…the United Kingdom is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible”. The Assembly voted 116 to 6 for the resolution, which said the British should withdraw their “colonial administration” from the Chagos Islands.
The embarrassing diplomatic defeat suffered by Britain highlighted the negative global opinion on maintaining colonial territories and it highlights the loss of influence by the UK in a changing geopolitical arena. The resolution is not binding and cannot be enforced; however its political strength should not be underestimated.
Sources: The Indipendent, UN officially demands Britain and US withdraw from Indian Ocean archipelago.
A legal analysis of the MPA in 2010: Colson D. A., Vohrer J., (October 2015), In re Chagos Marine Protected Area (Mauritius v. United Kingdom). The American Journal of International Law , Vol. 109, No. 4 (October 2015), pp. 845-851, Cambridge University Press. https://www.jstor.org/stable/10.5305/amerjintelaw.109.4.0845