The governments of Britain and Mauritius have reached a final deal to settle the future of the Chagos Islands but have been barred from signing it by a British judge.

Britain signed an agreement Thursday handing sovereignty over the contested and strategically located Chagos Islands to Mauritius, a move the government said ensures the future of a U.S.-U.K. military base that is vital to British security.

The Chagos Islands are in the middle of the Indian Ocean and home to a strategic military base on Diego Garcia.