Mauritius has gone to court to claim Britain used undue pressure to force it to give up the Chagos Islands in exchange for independence.
In 1966, the year after the UK got control of the Indian Ocean archipelago, it leased the biggest island Diego Garcia to the US.
America built an air base there, requiring the forced removal of around 1,500 people, and in the wake of 9/11 was controversially accused of using the island to detain – and even torture – terror suspects.
Mauritius’ case at the International Court of Justice got under way in The Hague on Monday.
“The choice we were faced with was no choice at all: it was independence with detachment (of the Chagos archipelago) or no independence with detachment anyway,” the minister mentor of Mauritius, Anerood Jugnauth, told the 14-judge panel.
The case comes after Mauritius asked the United Nations in 2017 to seek an advisory opinion from the ICJ.
The court’s decision will not be binding, but carries great influence under international law.
The case is seen by some as an important test of whether deals struck by colonial powers are legitimate given the power imbalance.
The UK is expected to argue that Mauritius is improperly using the international court to settle a bilateral dispute.
In 2016, Britain extended the US lease on Diego Garcia to 2036 and said the displaced islanders would not be around to return.