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The Right to Self-determination following the Chagos Archipelago Advisory Opinion

19 April 2021

By Jessica Honan – Research Assistant

The International Court of Justice (ICJ) produced the advisory opinion Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965 (Chagos advisory opinion) in 2019, which commented on the legality of Britain’s continual administration of the Chagos Archipelago in the Indian Ocean. There has historically been debate over which nation is sovereign over the archipelago, with Mauritius claiming since 1980 that, rather than the UK, it has the right to sovereignty. Originally a French colony in the 1700s, the archipelago was ceded to Britain at the end of the Napoleonic wars in 1814.

In 1965, the archipelago was illegally separated by Britain from the Mauritian territory to which it was attached. Mauritius was later granted independence, whereas Britain began expelling Chagossians from the archipelago in order for a US military base to be built. The UK has leased the base to the US until 2036, despite a series of legal decisions articulating the illegality of the UK’s actions. A series of domestic litigations in the UK has denied Chagossians repeatedly the right to return to their islands. The dispute over sovereignty is ongoing – Mauritius claims it maintains sovereignty over the territory due to the illegality of Britain’s actions in separating Chagos and Mauritius. Earlier in 2021, the International Tribunal for the Law of the Sea released a statement in favour of the Mauritian claim.

However, the Chagos advisory opinion, rather than clearly delineating which nation was sovereign of the archipelago, turned its mind to whether Britain was still a colonial power over the archipelago, and whether it has a legal obligation to decolonise the Chagos Archipelago on the basis of the existence of a Customary International Law (CIL) to the right to self-determination. CIL is unwritten international law that is nonetheless binding on States. It is formed by consistent State practice conforming to the rule, and opinio juris ­– that is, evidence that States believe themselves to be bound by the existence of such rules.

The ICJ looked at States’ actions, including through UN General Assembly resolutions, to determine that there was, in fact, sufficient state practice and opinion juris to crystalise the right to self-determination in CIL. As a result of this finding, the ICJ subsequently equivocated that the UK’s continual administration of the archipelago was illegal control. The UK was, therefore, held to be obliged to decolonise.

Yet despite this clear articulation of the UK’s obligations, the ICJ’s decision is not a binding judgment that can legally compel the UK to act. The ICJ’s decision was completed under the Court’s advisory jurisdiction, rather than as a contentious case between consenting State parties. Decisions under the Court’s advisory jurisdiction – that is, advisory opinions – are not legally binding on States and thus create no legal obligations for States to comply with their findings. Hence, the Chagos advisory opinion’s status means that Britain has scope to ignore the obligations arising from the Court’s acknowledgment of self-determination as a CIL.

There is, nonetheless, some significance to the Court’s decision, as it has contributed to the development of the law on self-determination. As well as the articulation that the right to self-determination is a law under CIL, the Court further qualified this right. First, the majority decision characterised the right to self-determination as a right erga omnes. The implication of this finding is that the right must be respected. This obligation does not necessarily require active steps to afford the right to self-determination, nor does it mean States are legally bound to comply. Critics of the ICJ’s decision suggest that this was a weak decision by the ICJ to deliberately avoid complex and potentially violent political disputes that could arise if minorities groups across the world believed the Chagos advisory opinion gave them some legal precedence to demand autonomy.

Moreover, the ICJ afforded the self-determination to peoples of a non-self-governing territory. This explicit correlation suggests that the right to self-determination and the right to decolonise were interconnected. This clearly identifies the right-holder as peoples ruled by colonial governance, thereby indicating that other peoples in non-self-governing territories are also intrinsically entitled to freedom from colonisation on the basis of the right to self-determination. This intertwining of the two concepts also limits the scope for non-colonial disputes to claim precedence from Chagos. In this way, the Court articulated the principle of self-determination as being secession to remedy an imperialist, external government, not cases of ethnic minorities wanting independence.

Whilst this jurisprudence may be non-binding, it is still considered to be authoritative. Under Article 38(1) of the ICJ Statute, advisory opinions are considered subsidiary sources and can substantiate and give weight to judicial decisions. Thus, whilst the decision in the Chagos advisory opinion creates no legally enforceable outcomes, its jurisprudence and its redefinition of the right to self-determination will be relevant to future ICJ decisions on self-determination.

Image: Salomon Atoll in the Chagos Archipelago (Source: Charles and Anne Sheppard via CC BY 3.0)

About Jessica Honan

Jessica Honan is a Bachelor of Laws (Honours) and Arts student at the Australian National University, majoring in Human Rights and French. Jess has interned with the Australian Institute of International Affairs, the Global Pro Bono Bar and is currently working on a project to legally enforce nuclear disarmament with the Micronesian Legal Clinic. Jess was awarded the National Council of Women Queensland Young Women Thinking Globally bursary in 2019. She is the current president of the International Relations Society at ANU and co-leads the ANU Law Reform and Social Justice Human Rights portfolio. She completed a tour to Cambodia to study transnational justice, and toured Myanmar under the Australian Government New Colombo Plan to research ethnic conflict. She speaks four languages, and her professional interests include the Law of Armed Conflict, transition justice and Human Rights law.