In 1968, Britain ethnicly cleansed the Chagos Archipelago to make way for a US military base on Diego Garcia. Since then, the Chagossians have been fighting through the courts for the return of their homeland. In 2009, in an effort to forestall future lawsuits, Britain declared the entire archipelago a Marine Protected Area, from whcih people (other than US military personnel) were banned. But now, the Permanent Court of Arbitration in The Hague has ruled that that was illegal:
Britain acted illegally in the way it has exercised territorial control over the Chagos Islands, a UN tribunal has ruled, raising questions over the UK’s claim to sovereignty and offering hope of return to hundreds of evicted islanders.
In a withering judgment, the UK is accused of creating a marine protected area (MPA) to suit its electoral timetable, snubbing the rights of its former colony Mauritius and cosying up to the United States, which has a key military base – allegedly used for the rendition of terrorist suspects – on the largest island, Diego Garcia.
The ruling effectively throws into doubt the UK’s assertion of absolute ownership, restricts the Americans’ ability to expand their facility without Mauritian compliance and boosts the chances of exiled Chagossians being able to return to their homeland.
A dissenting opinion from two of the five judges on the permanent court of arbitration at The Hague is even more scathing, stating that “British and American defence interests were put above Mauritius’s rights” both in 1965 when the British Indian Ocean Territory (BIOT) was established and in 2010 when the marine zone, which involves a ban on fishing, was set up.
This effectively unravels Britain's dirty colonial deal. They can't do anything to the Chagos without properly consulting Mauritius first, and they can't do anything contrary to the undertakings they gave. The ruling is binding in international law, though what that means in practice given the power disparity between the two parties is anyone's guess. But its still a victory for law over colonialism, and over Britain.
There's a summary of the judgement here.
