The U.K. has been ordered to return the Chagos Islands to Mauritius “as rapidly as possible” by the United Nations’ highest court, throwing the future of U.S. military base Diego Garcia into doubt. The International Court of Justice (ICJ) ruled that it was illegal under international law to separate the islands from Mauritius during the British decolonization of 1968. The decision by the ICJ is only advisory and the islands’ sovereignty will now be debated by the United Nations General Assembly. The ruling raises questions about the future of Diego Garcia—a vital U.S. base on the island that has been used as a landing spot for bombers that fly missions across Asia and purportedly a CIA blacksite for terror interrogations. Carl Schuster, a former director of operations at the U.S. Pacific Command’s Joint Intelligence Center, said: “Everything boils down to what Britain does... If it transfers the islands to Mauritius—and it has a history of obeying these rulings—then it’s up to Mauritius. If they say the existing agreement is no longer valid, then (the U.S.) would have to renegotiate.”