The Chagos Islands Legal Case Unraveled: Spectrum at the Center of a Storm

A political storm broke in the Commons this week after Labour ministers conceded that the so‑called “legal threat” underpinning the handover of the Chagos Islands was based on the United Nations Convention on the Law of the Sea (UNCLOS).

Defence Minister Luke Pollard told MPs that, without treaty consent, the UK “could have faced further legal rulings … legally binding … impacting our ability to protect the electromagnetic spectrum from interference” and undermining operational access to the Diego Garcia base.

Military Exemption Overlooked

Critics swiftly highlighted a glaring flaw: Article 298 of UNCLOS explicitly exempts “disputes concerning military activities” from its scope — a provision that appears to undermine the very foundation of the Government’s legal argument.

The Electromagnetic Spectrum Claim

Ministers have argued that, without legal certainty under the agreement, British and American access to the electromagnetic spectrum at Diego Garcia could be jeopardised. A Downing Street spokesman claimed that “the electromagnetic spectrum at the Diego Garcia base would not be able to continue to operate without a deal.”

Opponents counter that this rests on shaky ground. The International Telecommunication Union (ITU) — the UN body responsible for coordinating global radio frequencies — has no authority to adjudicate sovereignty disputes or disrupt existing military spectrum operations. Its own Radio Regulations state that their provisions “do not imply the expression of any opinion … on sovereignty or the legal status of any territory.”

Expert Dismissal

A Policy Exchange briefing dismissed the Government’s position as “baseless.” In his foreword, former security minister Tom Tugendhat wrote: “Every single defence of the deal … has proved to be baseless. It is past time … to walk away from the deal.”

Overstated Risks?

Diego Garcia’s strategic importance is undisputed. Ministry of Defence documents note that its electromagnetic capabilities underpin surveillance, satellite operations, communications, and wider UK–US power projection.

The UK’s Strategic Defence Review has also designated cyberspace and electromagnetic operations — “CyberEM” — as a distinct operational domain, with a dedicated command planned by the end of 2025.

Yet, critics argue, strategic importance does not justify invoking threats that lack credible basis. While a legal challenge from Mauritius could affect sovereignty claims, there is no mechanism under UNCLOS or ITU rules that would permit interference with the electromagnetic spectrum used at a joint military base.

In Brief

Labour has relied on UNCLOS to justify conceding the Chagos Archipelago, but has overlooked the treaty’s military exemptions. The Government’s claim that Diego Garcia’s essential electromagnetic spectrum access is at risk is now being questioned — even within defence circles.