The US government has blocked a British court hearing on the British Indian Ocean Territory (BIOT), citing security concerns. The hearing was to address the alleged unlawful detention of migrants on Diego Garcia, a highly secretive UK-US military base. Dozens of migrants had landed on the island in 2021, claiming that they were fleeing persecution and seeking asylum in Canada, but their boat had run into difficulties: they have been detained since then. On 9 July, the day before the hearing was due to start, the USA withdrew consent for lawyers and the BBC to access the island and refused to provide transport and accommodation, claiming that their visit posed ‘risks to the security and effective operation’ of the base. The cancellation is a severe setback for the migrants, who sought to demonstrate their detention conditions.