Immigration advocates sued the Trump administration on Wednesday in order to learn more about and communicate with detainees sent from the US to the tightly controlled American naval base in Guantánamo Bay, Cuba. Their lawsuit may shed light on both Trump’s secretive plans to vastly expand immigration detention at Guantánamo and the rights of immigrants sent there.

Long seen as a legal black hole, Guantánamo has historically evaded traditional government oversight, and immigrants previously detained there have faced mistreatment.

This lack of transparency takes on new urgency after Donald Trump issued an executive order last month to ramp up immigration detention capacity at the base with the intention of holding “high-priority criminal aliens unlawfully present in the United States.” He plans to eventually detain up to 30,000 immigrants there, up from the current capacity of about 120.

The Trump administration has not cited any legal authority justifying the new detentions, which reportedly have impacted at least some nonviolent “low risk” detainees — despite claims that the dozens of immigrants sent to Guantánamo so far are, as Defense Secretary Pete Hegseth put it, “the worst of the worst.” According to the Department of Homeland Security, they include members of the Venezuelan gang Tren de Aragua, which the federal government designated last year as a “transnational criminal organization.”

However, immigration attorneys representing three Venezuelan men charged with connections to the gang have argued in court that the accusations against them are false, suggesting that the same could be true of others sent to Guantánamo. On that basis, a federal court ruling last week

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