Dr Dan Boucher argues that the legal and political case being advanced for transferring sovereignty over the Chagos Islands to Mauritius rests upon a deeply flawed interpretation of international law and, in particular, upon an advisory opinion of the International Court of Justice that failed properly to account for the rights and status of the Chagossian people themselves. While supporters of the transfer present it as a necessary act of decolonisation and compliance with international law, Boucher contends that the process has instead produced a miscarriage of international justice by elevating the claims of Mauritius while marginalising the Chagossians, who lacked international personality and meaningful representation before the Court. In this article, he examines the principles of territorial integrity, self-determination, and decolonisation, arguing that the Chagos Islands should never simply have been presumed to form part of Mauritius and that the Chagossian people themselves should have been afforded the right to determine their political future through a referendum.
On 13 April, the UK Government announced that it was conceding that the Diego Garcia Military Base and British Indian Ocean Territories Bill could not become law and would fall at prorogation on 29 April because the United States, the principal user of the military base, had not agreed to the transfer of sovereignty to Mauritius.
This prompted considerable celebration, as many hoped that the Government would ultimately abandon its plans.
However, on 22 April, Jonathan Powell, the Prime Minister’s National Security Adviser, reassured the Prime Minister of Mauritius that the UK Government believed that the Bill still represented the best way forward and that it would reintroduce the legislation to transfer the islands to Mauritius just as soon as it could persuade the United States to do so. Mauritius welcomed this but also warned that it would not wait indefinitely.
In a context where the current UK government says it wants to transfer sovereignty because of an advisory judgement of the International Court of Justice and where Mauritius has warned that if the UK does not transfer it will bring a legal action based on that advisory opinion, a great deal of weight is being placed upon it. In this carefully argued piece, Dr Dan Boucher argues that to the extent that the advisory judgement is being used to justify the transfer of the Chagos Islands to Mauritius it amounts to a miscarriage of international justice because of errors made in the handling of the principle of ‘territorial integrity.’
International law, Territorial Integrity and a Miscarriage of Justice
It is not surprising that a considerable amount of time has been devoted to criticising the UK Government’s attempts to hand over the Chagos Islands to Mauritius on the basis that they have sought to justify this by reference to a particular determination of the International Court of Justice. There have been two problems. First, the ‘judgement’ was non-binding and second the court had no standing to make a judgement in any event. Disputes between Commonwealth member states are not dealt with through the ICJ.
The UK Government has sought to minimise these points by focusing on two others:
First, they have suggested that if we don’t comply, we will soon be subject to binding judgements from the International Tribunal on the Law of the Sea (ITLOS) which would render the Diego Garcia military base inoperable. This seems implausible given that ITLOS does not rule on sovereignty, as demonstrated by the recent 9 dash line judgement in relation to China and the Philippines, or on military matters.
Second, they have implied that regardless of whether the judgement is binding or not, we should simply lead by example and go the extra-mile in demonstrating our readiness to comply with international law, even when it does not strictly apply to us in this context.
In this article I want to address the latter argument and suggest that the Government’s enthusiasm for international law has caused it to lose sight of a critical point. International law is no more insulated against the possibility of miscarriages of justice than is domestic law. In the same way there can be miscarriages of justice in domestic courts, the same is possible in relation to the international courts. Indeed, this is far more likely when dealing with the non-binding judgements (in relation to which the relevant thresholds are lower) of courts that do not have proper standing to rule in any event.
The central problem with the non-binding Judgement in question is that a key party in the case, the Chagossian People, did not have international personality in 2018 and 2019 in the run up to the judgement and so their interests were not obviously afforded representation, profile and voice on a level playing field with the other parties. In any context, whether domestic or international, accommodating a court process where the different parties do not enjoy the same standing, and the same level of voice, constitutes an open invitation for a miscarriage of justice. In response to this some might point out that if a party lacks international personality, it is not possible for the court to give it to them so they can be considered on all fours with other parties that do enjoy international personality. In a case of this kind, however, the court should be alive to, and make allowances for: i) the impact of variations in the standing/profile/voice of the different parties in seeking to ensure a fair hearing, ii) the fact that the lack international personality of one actor may actually be a function of the presenting injustice that the court should call out and iii) the fact that that failure to do so is liable to result in victory for the party that already has international personality, regardless of whether or not that is the right outcome.
It is the purpose of this long read to argue that the decision of the court in 2019 constitutes a miscarriage of justice and that it set in train developments that have subsequently further compounded the initial wrong. In what follows this article will first consider four critical considerations that the court did not appear to engage with, no doubt in part because of the lack of proper Chagossian representation. Having risen to this challenge it will then unpack the consequence of their combined implication for the pursuit of justice as it relates both the Republic of Mauritius and the United Kingdom going forward.
I. The Four Considerations
1.Colonial Territorial Integrity is Provisional
While the Court did not pretend that the territorial integrity of colonies/former colonies is frozen in time, (that is not even true of sovereign states, as demonstrated by Czechoslovakia becoming the Czech Republic and Slovak Republic), it locked on to the sensitivities pertaining to colonial powers changing the boundaries of colonies in the run up to decolonisation in a way that lacked balance and, as we shall see, prioritised the interests of the party with international personality over the party without international personality. In truth the concerns about making changes to colonial boundaries before decolonisation were not the result of a conviction that colonial powers were endowed with special wisdom in determining the boundaries of their colonies such that they should not be questioned. Indeed, it was readily appreciated that because colonial powers had less of a stake in the boundaries of their colonies than in their own boundaries, that they would likely afford considerably less care and attention to the former than the latter. There was, however, a concern that a colonial power that had been persuaded to give up a territory may, as a final expression of imperial leverage, seek to change its boundaries before formal decolonisation for reasons pertaining to its own self-interest rather than that of the people of the colony. The 1960 Declaration on Decolonisation recognised this risk and made it clear that any changes made to the territorial integrity of a colony must be the result of the genuine and free decision of the people of the territory. Thus, the point was never that they could not change their boundaries. It was expected that many would, see UN Resolution 567 (VI), 648 (VII) and 742 (VIII), precisely because those boundaries had been imposed. Instead, the point was that the changes should be made freely by the indigenous people and not by the colonial power.
- 2.The Territorial Integrity of Mauritius and Chagos Islands – Dubious in Practice
Following on from the above, the Court failed to recognise the obvious point that if ever there was a case of colonial boundaries that were highly unlikely to survive self-determination, they were those of the pre-November 1965 colonial unit covering Mauritius and the Chagos Islands. In the first instance, the distance between the two was over a thousand miles, comparable to that between Kent and North Africa. In the second instance, not surprisingly, the islands were populated by different people groups: the Chagossians were black Africans, while the Mauritians were majority Indians. In the third instance, the Mauritians greatly outnumbered the Chagossians, meaning that if a Republic of Mauritius and the Chagos Islands had been formed in 1968, the Chagossians would have been condemned to being a permanent tiny minority, rather than a small nation in their own right. Finally, in the fourth instance, the sense in which the Chagossians cannot be regarded as the same people as the Mauritians has been greatly compounded by developments since 1964/5 because the Mauritians did not consult the Chagossians about their forced removal, but rather acquiesced with it in agreeing to provide one of the key places to which the Chagossians were forcibly removed. In this regard it is hard not to acknowledge the critical distinction made by the Chagossian First Minister, Misley Mandarin, between the Chagossians and the Mauritians in the following:
‘The people of Mauritius were not forcibly removed from their islands between 1968 and 1973. In fact, they made themselves an accessory to our forced removal agreeing to be the place to which we were forcibly removed. …Had the Mauritians been our brothers and sisters they would have no more tolerated the events of 1968-73 than would the true mother of the baby boy presented to King Solomon have permitted his being cut in two.’[1]
- 3.The Timing of Self-Determination
Then it is important recognise that in international law there is no imperative for the self-determination process – which might change the territorial integrity of a territory – to happen after decolonisation, as has often been implied. Self-determination and consequent changes in territorial integrity can happen before or after decolonisation, so long as the self-determination process faithfully expresses the will of the indigenous people, without interference by the colonial power. This point is recognised both by the International Court of Justice Non-Binding Judgement and by international practice.
- The International Court of Justice
The Court stated in its non-binding judgement:
‘Having reviewed the circumstances in which the Council of Ministers of the colony of Mauritius agreed in principle to the detachment of the Chagos Archipelago on the basis of the Lancaster House agreement, the Court considers that this detachment was not based on the free and genuine expression of the will of the people concerned.’[2] (Para 172) (Bold added)
The clear implication of this is that had detachment ‘been sanctioned by the free and genuine expression of the will of the people concerned’ the detachment would have been valid.
- International Practice
The appropriateness of colonies changing their territorial integrity through ‘the free and genuine expression of the will of the people concerned’ before decolonisation, can also be seen in international practice courtesy of the case of the Gilbert and Ellice Islands, whose profile and experience in many ways parallels that of Mauritius and the Chagos Islands. While Mauritius and the Chagos Islands are separated by 1339 miles, the Gilbert and Ellice Islands were separated by 800 miles; while Mauritius and the Chagos Islands are populated by different people groups: majority Indian (Mauritius) and Black African (Chagos), the Gilbert and Ellice Islands were populated by a Micronesian people (Gilbert Islands), and a Polynesian people (the Ellice Island) and while the Mauritians were much more plentiful than the Chagossians, the residents if the Gilbert Islands were similarly more plentiful than the residents of the Ellice Islands.
In this context, before their decolonisation, the representatives of the Ellice Islands told the UK Government that they did not want to become part of a new sovereign state of the Gilbert and Ellice Islands because the residents of the Gilbert Islands were from a different people group and far more numerous, such that the residents of the Ellice Islands would be constantly condemned to being in a minority. The UK Government responded by offering the Ellice Islands a self-determination referendum with the options of remaining joined to the Gilbert Islands or becoming separate. The residents of the Ellice Islands voted, by a clear majority, for separation, becoming, first, a separate colony and then, two years after that, a new independent state, called Tuvula. The Gilbert Islands, meanwhile, became the Republic of Kiribati the following year.
- 4.A Colony of a Colony
Finally, while it was entirely appropriate for the residents of the Ellice Islands to request, and be provided with, a self-determination referendum ahead of decolonisation, the provision of a self-determination referendum for the Chagossians in 1965 was, and going forward will be, imperative. In order to understand why, it is necessary to gain a better understanding of the territorial integrity of the pre-November 1965 colony.
The truth is that ‘territorial integrity’ is not a simple given physical res extensa, but something that is peopled, according to certain international relations principles and is, in part, socially constructed. While an asserted territorial integrity will cover an extent of territory, it does not follow that this is coextensive with a valid territorial integrity. This point is highlighted for us by UN resolutions 567 (VI), 648 (VII) and 742 (VIII) which help define the basis of a valid and invalid territorial integrity. They are clear that this must be informed by the absolute civic equality of everyone across the country. Specifically, they state that ‘self-government can …be achieved by association with another State or group of States if this is done freely and on the basis of absolute equality.’ (Bold added).
One might be tempted to limit this appreciation of territorial integrity to the immediate subject at hand, namely the creation of a new valid territorial integrity for the purpose of independent sovereign statehood, but the principles set out above must shape how one views all valid assertions of territorial integrity that need not immediately be called into question. Even while an historic colony will not have been created by a self-determination referendum in the first instance, there is a sense in which the territorial integrity of the colony coheres to the extent that, if one removes the impact of the colonial imposition, the remnants of citizenship left behind are such that, as far as the indigenous people are concerned, they all relate to each other on the basis of civic equality. Indeed, this may have roots that stretch back to earlier times if the residents of the said territory effectively existed as a people in some form prior to colonisation.
The existence of this basic equality between a colonial people, which bestows upon them something they enjoy in common, does not necessarily mean that in moving towards decolonisation the territorial integrity of the colony will hold. It may be that, notwithstanding the civic equality, such as it exists, there are other cultural and social cleavages beyond a common civic bargain (which opens the door to a single political nation), that might still necessitate a reconfiguration of territorial integrity. However, in a context where the boundaries of a colony are such that they do not inform a common civic experience, then even before considering the possibility of other social cleavages, they cannot be said to constitute a territorial integrity. This was the experience of Mauritius and the Chagos Islands in 1965.
In the pre-November 1965 colony, the Chagossians were not treated equally with the Mauritians because they were afforded no representation in the Mauritian Council of Ministers, and even the language of the judgement recognises that the Chagos Islands were actually a ‘dependency of Mauritius’ (Para 28).’[3] The word ‘dependency’ is deployed to refer to the relationship between the people of a territory, that is conceived for some purpose as being part of a more immediate territory, wherein the people of the wider territory do not enjoy citizenship on a par with the people of the immediate territory in respect of which their dependent relationship is expressed. It implies that rather than being a genuine part of Mauritius, the Chagos Islands were in fact for some key purposes separate, effectively existing as a colony of a colony. In this the standing of the Chagos Islands stood in stark contrast to that of the Ellice Islands which were represented within the colonial governance structures. While the Ellice Islands returned 4 members of the House of Representative of the Gilbert and Ellice Islands and the more populous Gilbert Islands returned 19, the Chagossians had no representation in the Mauritian Council of Ministers whatsoever. Indeed, this is even conveyed in the names of the respective colonies. While the Chagos Islands were not acknowledged in the name, the Colony of Mauritius, the Ellice Islands were very much visible in the Colony of the Gilbert and Ellice Islands. The lack of standing of the Chagos Islands is similarly reflected in the decision to call the Treaty between the UK and Mauritius regarding the Chagos Islands, ‘the Mauritius Treaty’!
Thus the critical point to make here is that if, even before decolonisation, the socially constructed nature of the colonial territorial integrity is such that it does not afford a common experience of colonial citizenship, (and actually creates two classes of ‘colonial citizens’ between different parts of the territory), there can be no defaulting to a single political nation on decolonisation, ahead of self-determination. Rather, there should be a presumption that, prior to decolonisation, those subject to the lesser citizenship should be afforded a robust self-determination referendum to first establish whether they wish to be joined to the rest of the colony at decolonisation or whether they wish to decolonise as a separate entity.
Moreover, this imperative is greatly compounded in a context where a putative territorial integrity is negated by the impact of a territorial fault line between one effective level of ‘colonial citizenship’ and another, when that fault-line also coincides with, both a distance of over a thousand miles and the existence of different dominant people groups, as in the case of the place of the Mauritians, on the one hand, and the Chagossians, on the other in 1965. That imperative becomes even more pronounced when considered in light of the events between 1968 and 1973, and the role played by Mauritius as a party to the forced removal of the Chagossians, which render the assertion that the Chagos Islands can be regarded as part of the same territorial integrity as Mauritius, absurd.
II. The Application of the Four Considerations
Having set out the four considerations, they can now be brought together to draw out the following conclusions. First, that far from being set in stone the territorial integrity of colonies is more provisional than that of sovereign states which can self-determine to change their boundaries. Second, that if ever there was a colony with a highly uncertain territorial integrity that was likely to self-determine to adopt different boundaries it was the pre-1965 colony of Mauritius and the Chagos Islands because of the distance and differences between the two. Third, there is nothing wrong with a colony changing its territorial integrity before decolonisation, so long as this is expressed freely through a credible self-determination mechanism, as effectively recognised both by the Court and by international practice. Finally, while it was entirely appropriate to respond positively to the request of the residents of the Ellice Islands for a self-determination referendum before decolonisation, the provision of a self-determination referendum for the Chagossians should have been the default position in 1965 – and going forward – because the territorial integrity of the colony of Mauritius and the Chagos Islands was already fractured in the sense that it did not sustain a common colonial citizenship, but treated one part of the colony as a dependency of the other. Put another way, the need to provide the Chagossians with a self-determination referendum in 1965 was far greater than in the case of the Ellice Islands, which enjoyed proper representation within the governance of the colony of the Gilbert and Ellice Islands, and thus an absolute equality within the civic bargain, such as it existed, which meant there was some basis for asserting a valid territorial integrity for the Gilbert and Ellice Islands as a whole.
In this context the conduct of Mauritius is plainly problematic in a way that the International Court of Justice should have been able to see:
In the first instance, the Mauritian Council of Ministers did not consult the Chagossians before agreeing to the British proposal to separate the Chagos Islands from Mauritius.
In the second instance, the Mauritians then acquiesced with the then UK Governments and became a party to the forced removal of the Chagossians by agreeing to provide one of the main places to which they were forcibly removed.
In the third instance, and in some ways of greatest concern given their role in the forced removal of the Chagossians and clear desire to obtain the Chagos Islands, the Mauritians have now effectively utilised the fact that the Chagossians were forcibly removed, between 1968 and 73, to seek to secure the islands without needing to have a self-determination referendum. This point becomes even more concerning – as we will see shortly – when we consider the conduct of Mauritius in the period since the non-binding Judgment.
Looking Beyond the Court Case
In order to really appreciate the difficulties arising from the non-binding ICJ judgement, however, we need to look beyond it to the subsequent developments that have flowed in its wake. Both the Governments of Mauritius and the UK have been very clear that the Mauritius Treaty, signed on 22 May 2025, constitutes the course of action necessary to complete decolonisation and comply with the findings of the court.
One might have hoped that what the International Court of Justice had in mind in bringing its judgement was that the Chagos Islands should be ‘returned’ to Mauritius so that it could then resettle the Chagossians and afford them a right of self-determination. However, the Mauritius Treaty makes no such provisions. It fails on multiple counts including:
First, and contrary to the assertions of some (which have likely resulted in some Chagossians being persuaded to support the deal on false pretences), it does not provide a Chagossian right of resettlement. There is no legal commitment to resettle any Chagossians on their islands and interestingly in February, rather than celebrating the return of 4 islanders to Peros Banhos for the first time since the removal of the Chagossian people in 1973, the Mauritian Government reacted angrily, accusing them of ‘illegality.’
Second, the treaty makes no provision for a self-determination referendum for the Chagossian people to confirm whether they wish to be part of Mauritius or a resettled British Overseas Territory. One of the most disturbing aspects of this failure is the fact that the UK Government did not insist on these two points. Instead, the Prime Minister signed a treaty that leaves wide open the possibility of the Chagossian people being denied both self-determination and resettlement on their islands.
In this context the UN Committee on the Elimination of Racial Discrimination intervened and rather than simply expressing concerns about the content of the Mauritius Treaty called on the UK Government and Government of Mauritius not to proceed with ratification but to go back to the drawing board with a plan that has the Chagossians at its heart. They were particularly damning of the failure of the treaty to commit either to a Chagossian right of resettlement or a Chagossian self-determination referendum.[4]
International Personality
As acknowledged by the introduction, the key problem with the ICJ process has been the failure to make allowances for the fact that while one key party, the Mauritians, could engage with the court as a bearer of international personality, the other key party, the Chagossian, had no such standing. Quite apart from anything else, while the Mauritians had at their disposal the resources of a state through which to seek the very best legal advice, the Chagossians had no such opportunity. In this context, the concerns that the UK Government backed the Mauritian rather than the Chagossian perspective because the top lawyer the Mauritians were able to secure is close to the Prime Minister and Attorney General, necessarily, become more troubling.
It was in this context, and given the failure of the UK Government to listen, that over the weekend of 13 and 14 December 2025, elections were held and a Chagossian Government in Exile, led by First Minister Misley Mandarin was formed in order to provide the Chagossian people with a platform from which they can seek to acquire international personality and a voice in their own right. While they could seek, from this point, to become a fully sovereign state, the Chagossian Government in Exile has made it plain that this is not its purpose. They want the Chagos Islands to be a resettled British Overseas Territory, with the ongoing US-UK military base on Diego Garcia, and consequently will only exist as a Government in Exile until such a time as: i) there is a proper self-determination referendum for the Chagossian people in which being a resettled British Overseas Territory is an option, and ii) the results of the referendum have been honoured.
This approach will have wider benefits for both the United States and Tuvula.
In the first instance, given that polling suggests that any self-determination referendum would result in the Chagossian people electing to be a resettled British Overseas Territory, the provision of the referendum would result in the whole archipelago remaining under British sovereignty. It would thereby resolve the much-discussed geo-political problems associated with transferring the Islands to Mauritius in: i) creating a power vacuum beyond Diego Garcia and ii) constraining the operations of the Diego Garcia base courtesy of the Pelindaba Treaty.
In the second instance, the provision of the referendum would also help Tuvula because the failure to require a Chagossian self-determination referendum would, for the reasons set out in this paper, place something of a question mark over the Ellice Islands referendum. Every effort should be taken to prevent such an eventuality.
Dr Dan Boucher PhD
Dr Boucher has a PHD in sovereignty and international relations.
[1] https://parliamentnews.co.uk/chagos-islands-first-minister-pleads-for-the-lords-to-reject-diego-garcia-bill
[2] https://www.icj-cij.org/sites/default/files/case-related/169/169-20190225-ADV-01-00-EN.pdf
[3] https://www.icj-cij.org/sites/default/files/case-related/169/169-20190225-ADV-01-00-EN.pdf
[4] ttps://tbinternet.ohchr.org/_layouts/15/treatybodyexternal/Download.aspx?symbolno=INT%2FCERD%2FEWU%2F11263&Lang=en
