Bancoult, R (on the application of) (No 3) v Secretary of State for Foreign and Commonwealth Affairs (Respondent)

Factual and Procedural Background

The Appellant is chair of a refugees’ group representing Chagossians who were removed from the British Indian Ocean Territory (BIOT) between 1971-1973. In 2010 the BIOT Commissioner, acting on ministerial instruction, issued a proclamation establishing a “Marine Protected Area” (MPA) covering a pre-existing 200-mile environmental zone. The proclamation was accompanied by a ministerial statement indicating that commercial fishing would be banned, effectively creating a “no-take” reserve.

The Appellant sought judicial review on two grounds: (1) that the MPA was motivated by an ulterior purpose—to make any future Chagossian resettlement impracticable; and (2) that the public consultation preceding the proclamation was unlawful because it failed to reveal arguable Mauritian in-shore fishing rights. The Administrative Court rejected both grounds; the Court of Appeal affirmed but differed on one evidential ruling; and the Supreme Court granted limited permission to appeal.

Legal Issues Presented

1. Whether the decision to establish the MPA was vitiated by an improper purpose aimed at frustrating potential Chagossian resettlement.
2. Whether the consultation process was unfair because it omitted reference to arguable Mauritian traditional fishing rights.
3. Whether a leaked United States diplomatic cable was inadmissible because of the inviolability of diplomatic archives under the Vienna Convention on Diplomatic Relations 1961.

Arguments of the Parties

Appellant's Arguments

• The leaked cable showed that senior BIOT officials viewed the MPA as a means to “put paid” to resettlement, demonstrating an improper motive.
• Failure to disclose possible Mauritian fishing rights deprived consultees of material information, rendering the consultation unlawful.
• The cable, already in the public domain, was admissible; excluding it curtailed effective cross-examination and undermined a fair hearing.

Respondent's Arguments

• The Foreign Secretary’s decision was based on legitimate environmental considerations, not on preventing resettlement.
• No enforceable Mauritian fishing rights were believed to exist; consultees could themselves raise the point, so consultation was adequate.
• The cable was protected by diplomatic inviolability and, in any event, would not have changed the outcome.

Table of Precedents Cited

Court's Reasoning and Analysis

Admissibility of the Cable: The majority held that diplomatic archives are generally inviolable (Vienna Convention, arts 24 & 27(2)), but that protection ceases when (a) the document is no longer within the mission’s archive, and/or (b) the material is already in the public domain. Because the cable had circulated beyond the London mission and was published world-wide via Wikileaks and newspapers, inviolability no longer applied, so the Court of Appeal had been right that the cable was admissible.

Effect of Exclusion: Although the cable should have been admitted, the Supreme Court majority accepted the Court of Appeal’s view that its absence could not realistically have altered the Administrative Court’s findings. Extensive cross-examination had already explored its contents; the contemporaneous documents showed the Foreign Secretary was motivated by environmental considerations and pre-election political timing, not by a scheme to bar resettlement.

Improper Purpose Allegation: The Court examined correspondence, meeting notes and witness evidence. It accepted that a government official had told U.S. counterparts the MPA would make resettlement difficult, but found this reflected a practical consequence rather than a hidden motive. The decisive actor was the Foreign Secretary, who was “fired up” by conservation benefits and overrode officials’ procedural caution. Even assuming a civil servant’s collateral motive, there was no evidence it influenced the minister’s decision.

Consultation on Mauritian Fishing Rights: Legal advice available to officials was that Mauritius had no enforceable in-shore rights. Mauritius declined to engage with the consultation, and other stakeholders did raise fishing concerns. The majority concluded the omission did not render the process unfair, especially as subsequent international arbitration on those rights lay outside the domestic review.

Dissent: Judge Kerr (with Judge Hale concurring) reasoned that admitting the cable could have affected the fact-finding: the document directly contradicted key witnesses and might have shown an undisclosed objective to block resettlement. They would have remitted the matter for reconsideration with the cable in evidence.

Holding and Implications

HELD: The appeal is DISMISSED; the cross-appeal on diplomatic inviolability is also DISMISSED. Permission to appeal on fishing-rights issues was granted but the appeal on that ground likewise fails.

Implications: The MPA proclamation and associated no-take policy remain in force. The decision clarifies that leaked diplomatic documents can be admitted in UK courts once widely public, but their exclusion will not invalidate proceedings unless there is a realistic possibility of a different outcome. No new substantive precedent on resettlement or fishing rights was set, though an ongoing international arbitral award concerning Mauritian rights may prompt future policy adjustments.