The willingness of the courts to review powers exercised under the royal prerogative was reaffirmed in the decision in the case of the Chagos Islanders. The Court of Appeal upheld the decision of the Divisional Court to quash an Order in Council which had the effect of preventing the former inhabitants of the Chagos Islands from returning to the islands from which they had been compulsorily removed in the 1970s.


The Chagos Islands, which had been ceded to Great Britain by France in 1814, form part of the British Indian Ocean Territory; a separate colony governed by or under Orders in Council made in the exercise of the prerogative power of the Crown. Under an Immigration Ordinance made in 1971 the inhabitants of the Chagos Islands were compulsorily removed, mainly to Mauritius, because Diego Garcia, the principal island in the archipelago, was required for use as a United States military base. The 1971 Ordinance had been quashed by the Divisional Court in 2000 on the ground that the exclusion of an entire population from its homeland lay outside the purposes of the parent Order made in 1965 by which the Chagos Islands has been constituted as a separate colony. The Government stated that it accepted the court's ruling and would not appeal. However, the government later decided that resettlement was not feasible and that the territory was still wanted for defence purposes. In 2004, an Order in Council was made which had the effect of preventing the Chagossians from returning home. The Divisional Court held that the Order was invalid. The Secretary of State appealed on the following grounds:

  • any attack on the validity of a colonial Order in Council made under the royal prerogative was precluded by the Colonial Laws Validity Act 1865;
  • the government of a ceded colony by Order in Council was not a ministerial act but a sovereign act of the Crown, challengeable only on the ground of incompatibility with imperial legislation.

The Decision

In relation to the first ground of appeal, the Court of Appeal found that the 1865 Act had neither the purpose nor the effect of barring challenges to the acts of ministers in the exercise of the royal prerogative. The purpose of the Act was to resolve any doubts concerning the validity of colonial laws that might arise through a conflict between those laws and any other superior legal provision. In this case, the Court found that the question of a conflict between laws was secondary to the principal question of whether the 2004 Order which prevented the Chagosssians from returning home was lawful in the first place. Accordingly, the challenge to the validity of the Order was not barred by the 1865 Act.

The Court's response to the second ground of appeal demonstrated the judiciary's refusal to allow measures enacted under the royal prerogative to enjoy generic immunity from judicial review. Although an Order in Council is formally made by the Monarch under the prerogative, the Court was quick to recognise that, in reality, it is an act of the executive and as such is amenable to any appropriate form of judicial review.

In recognising the amenability of an Order in Council to judicial review, the decision continues the expansion of judicial review into areas previously thought to be beyond its reach. The judgment contains support for the view that the limits which have previously been placed on the judicial oversight of prerogative and other non-statutory powers can be overcome in pursuit of the overriding objective of preventing the abuse of power by governmental or quasigovernmental bodies.

Abuse of Power

Having held that the making of the 2004 Order was susceptible to judicial review, the Court of Appeal considered whether or not that Order had, in fact, been lawfully made. The following grounds of challenge were considered: 

  • that it was ultra vires – i.e. it was outside the scope of colonial governance of the British Indian Ocean Territory;
  • that it was irrational;
  • that it breached the Chagos Islanders' legitimate expectation of a right of return.

In his judgment, Lord Justice Sedley concluded that the permanent exclusion of an entire population from its homeland for reasons unconnected with their collective wellbeing could not fall within the scope of the prerogative power of colonial governance. Lord Justice Waller and Sir Anthony Clarke did not go so far, and declined to comment on the breadth in law of the Crown's colonial powers.

The judges agreed, however, that the making of the 2004 Order was unlawful on the basis that it breached the islanders' legitimate expectation that they would be allowed to return to their homeland. That expectation had arisen from the Government's response to the quashing of the 1971 Immigration Ordinance. Shortly after the Ordinance was quashed, the Foreign Secretary, Robin Cook, issued a written statement accepting the judgment and announcing that a new Ordinance would be put in place which would allow the Chagossians to return.

Adopting the typology of legitimate expectation cases which had been developed in R v North Devon Health Authority ex p Coughlan [2001] QB 213, the Court held that Robin Cook's statement had induced a legitimate expectation among the exiled islanders of a benefit that was substantive and not simply procedural. Coughlan established that where a legitimate expectation of this type has arisen, the frustration of that expectation will be unfair unless there is an overriding interest to justify a departure from what has previously been promised. In this case, the Court of Appeal found no overriding interest that could justify the Government's change of policy, and accordingly found that the frustration of the islanders' expectation of a right to return was so unfair as to amount to an abuse of power. The appeal was dismissed.