International Court of Justice and UN General Assembly do not alter the outcome of the Chagos Islands challenge

R (Hoareau) v Secretary of State for Foreign and Commonwealth Affairs [2020] EWCA Civ 1010

19 August 2020

In a February 2019 Advisory Opinion, the International Court of Justice stated that, under international law, the decolonisation of Mauritius by the UK has never been lawfully completed and the UK must therefore “end its administration” of the Chagos islands. In May 2019, the UN General Assembly passed a resolution endorsing that position.


These events on the international plane gave hope to the displaced Chagossians in their domestic struggles before the UK courts. However, the Court of Appeal has now confirmed that the UK government acted lawfully in deciding to compensate the Chagossians instead of granting their calls for resettlement.

The judicial review challenge

When it granted Mauritius independence in the late 1960s and early 1970s, the UK government created, and retained dominion over, an area of ocean it called the ‘British Indian Ocean Territory’. This territory included the Chagos archipelago. The largest of the islands in the archipelago, Diego Garcia, was subsequently leased to the United States as a military base. The entire population of the Chagos Islands was exiled from the archipelago, and some settled in the UK.

Since at least the early 2000s, a protracted legal battle has raged in the domestic and international courts to determine some of the consequences of these events. The Chagossians have been refused a right of abode in the Chagos archipelago, and some have been paid compensation instead. In the domestic courts, the Chagossians’ current case is a judicial review challenge fought on grounds that the UK government’s refusal to grant them a right of abode has breached their rights under Articles 8 of the European Convention of Human Rights (“ECHR”) (which protects private and family life, home and correspondence), as well as Article 1 of the First Protocol (“A1P1”) (which protects a person’s peaceful enjoyment of possessions).

The Chagossians also argued that the right to self-determination and resettlement constitute customary international law (“CIL”). Their view was that CIL ought to be regarded as decisively influencing the scope of equivalent domestic common law protections. Another argument advanced by the Chagossians was that their fundamental rights were at stake, so the court should have scrutinised vigorously the government’s rationale for deciding to refuse them a right of abode in the Chagos archipelago (applying the standard of ‘anxious scrutiny’). Finally, the Chagossians argued that the government’s decision was unlawful on grounds of irrationality because relevant matters had not been taken into account or relevant facts had been mis-described.

In its judgment, the Court of Appeal considered whether the Divisional Court below had been correct to reject the above arguments in 2019.

International law

The primary Chagossian argument relied heavily on the Advisory Opinion of the International Court of Justice (“ICJ”) (the principal judicial organ of the United Nations system); and the subsequent resolution of the UN General Assembly (the “General Assembly”) (the main deliberative, policymaking and representative organ of the United Nations system). By contrast, the UK government contended that, if it was relevant at all, the Advisory Opinion did not state that the ECHR extended to the Chagos archipelago and did not identify any right that the Chagossians as individuals could exercise domestically against the UK. These were rights exercisable only by states on the international plane.

These arguments relate to the dualist nature of the UK legal system, under which domestic law and international law are treated as separate. In summary, international law can only be relied upon before the UK courts if it is incorporated into domestic law or if it influences the interpretation of rights and obligations that exist in domestic law. Whereas the Chagossians invited the Court of Appeal to be strongly influenced by the Advisory Opinion and General Assembly resolution, the UK Government argued that, properly analysed, these instruments had minimal domestic relevance.

The Court of Appeal judgment

A panel comprising the Master of the Rolls and Lords Justice Green and Dingemans co-wrote their unanimous judgment. Their conclusions on each of the key arguments are summarised below.

Was the ECHR applicable?

To prove a violation of Article 8 or A1P1 the Chagossians first had to demonstrate that the British Indian Ocean Territory fell within the jurisdiction of the ECHR, under either Article 1 (the state's duty to secure ECHR rights to everyone within its jurisdiction) or Article 56 (under which a state may declare that the ECHR extends to overseas territories for whose international relations it is responsible). Articles 1 and 56 were considered by the European Court of Human Rights in Al-Skeini v United Kingdom (2011) 53 EHRR 18 and were held to be mutually exclusiveIt was Article 56 that applied here because the British Indian Ocean Territory was an overseas territory, but the required declaration had not been made. ECHR rights had therefore not been extended to the Chagos archipelago.

In coming to this conclusion, the Court of Appeal rejected the suggestion that the Advisory Opinion and the General Assembly resolution rendered void the UK’s past acts in the British Indian Ocean Territory. This was apparent because the ICJ was clear that it had not found any breach of peremptory norms of international law. The Advisory Opinion and General Assembly resolution were prospectively worded and forward looking in effect. That meant the UK would remain responsible for the international relations of the British Indian Ocean Territory until decolonisation was complete. Until then, only the UK could make an Article 56 declaration.


Did the ICJ or General Assembly identify breaches of ECHR rights?

In its judgment, the Court of Appeal explained that an Advisory Opinion of the ICJ is not a judgment with binding effect determining any dispute between particular parties. It is a non-binding opinion. In this case it is addressed to the General Assembly, which is responsible for acting upon it. The Advisory Opinion must therefore be read alongside the subsequent General Assembly resolution putting it into practice.

The Advisory Opinion states that the General Assembly has a measure of discretion over how the international law right to self-determination should be realised. The General Assembly resolution exercises that discretion by demanding that the UK “withdraw its colonial administration from the Chagos Archipelago unconditionally within a period of no more than six months…” and urging cooperation between the UK and Mauritius to facilitate resettlement of Mauritian nationals, including Chagossians, in the British Indian Ocean Territory without impediment. The resolution also calls upon UN Member States to ensure the completion of the ongoing decolonisation process and recognise the Chagos archipelago as an integral part of Mauritius.  

On this basis, the Court of Appeal pointed out that, in substance, the Chagossians’ judicial review was focussed on resettlement, but the Advisory Opinion and the General Assembly resolution were concerned instead with the completion of the decolonisation process. While these international law instruments recognised a human right relating to resettlement, they did not address that right’s relationship with Article 8 ECHR or A1P1. The consequences were left to be determined later “during the completion of the decolonisation process”. In light of this, the Court of Appeal concluded that, given the UK is a dualist system, the rights of self-determination and decolonisation referred to in these international law instruments were exercisable only by one state against another and not domestically. Nothing in them granted resettlement rights to the Chagossians themselves, as individuals. Indeed, far from the UK being required to grant anyone a right of abode in the Chagos archipelago, it was instructed to decolonise the archipelago forthwith.


Enlarged common law right of abode?

The same substantive analysis of the Advisory Opinion and General Assembly resolution also led the Court of Appeal to reject the Chagossians’ argument that a CIL right of resettlement had been enunciated capable of enlarging the domestic common law right of abode to have an equivalent scope. Any such common law right would, in any event, be overridden by legislation and, here, legislation expressly prohibited the return of the Chagossians to the British Indian Ocean Territory.


Anxious scrutiny and irrationality

Following R v Ministry of Defence ex parte Smith [1996] QB 517, ‘anxious scrutiny’ is the expression used to capture the idea that particular features may justify the court in subjecting an administrative decision to a closer and more rigorous standard of review regarding its rationale than would otherwise be the case in a rationality challenge. Such high-intensity review has the effect of diminishing the weight or respect given by the court to the evaluative judgment and assessment made by the primary decision-maker. The greater the intrusion into the rights of individuals, the more closely the court will examine the reasoning behind it. The more important and consequential for individuals the decision may be, the more care is likely to be required of the decision maker to render it rational.

The Chagossian case was that ‘anxious scrutiny’ was required, and the absence of a formal statement to the effect that it had occurred showed it had not. The Court of Appeal held, however, that a failure to invoke ‘anxious scrutiny’ “does not mean that the Court will not look long and hard at the decision challenged in the case”. The Divisional Court had done just that. The decision being challenged had itself been taken at the highest level of government, involving the Prime Minister, Foreign Secretary and National Security Adviser and the court concluded, obiter, that it had been “taken with conspicuous care and consideration”.

The final Chagossian argument was that the decision maker had failed to take account of relevant information and proceeded on the basis of facts that were so mis-described as to defeat the decision. The Court of Appeal rejected this because the Divisional Court’s factual findings had been based on the full spectrum of the evidence while the evidence before the Court of Appeal was narrow. It would only interfere to correct a demonstrable misunderstanding of relevant evidence, or failure to consider it. This was found not to apply to the misstatements alleged by the Chagossians.



This case adds to the trend of international law increasingly being deployed in judicial review challenges before the courts of England and Wales. It also demonstrates the difficulties parties face in seeking to persuade judges to give effect to international law. The influence of CIL on the common law remains in flux, and, more generally, only international law rights incorporated into domestic legislation can be relied upon. In this case, the court carefully scrutinised whether the international instruments before it really represented a touch-point between the domestic and international legal systems.

This case is also a good example of how difficult it is to succeed in irrationality challenges, especially against high profile politically inflected decisions taken at the highest level in the expectation of challenge. This is likely to be so whatever the standard of review, and this judgment is a helpful reminder that whether anxious scrutiny has occurred is a matter of substance, not of form.

Further information

Kingsley Napley LLP regularly represents parties in judicial review challenges. Our lawyers also blog regularly about public law matters. Follow our Public Law blog for the latest commentary.

Should you have any questions about the issues covered in this blog, please contact Adam Chapman or a member of our Public Law team.


About the author

Nick Wrightson is a Senior Associate in our Public Law team. Nick has an administrative and public law practice focused on judicial review litigation and supporting clients through public inquiriesNick’s experience includes representing public bodies, private companies, individuals, representative bodies and charities – often in high stakes, politically and commercially sensitive cases.


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