The US Supreme Court on October 1, 2026 agreed to hear a challenge to a Trump administration policy that subjects millions of immigrants living in the United States illegally to mandatory detention during their deportation proceedings.

The case arrives at the top US judicial body as the latest legal battle over President Donald Trump's hardline immigration agenda, and it addresses an issue that has divided lower courts amid numerous lawsuits by migrants and advocacy groups. The policy forms part of a broader set of measures the administration has adopted in pursuit of Trump's goal of mass deportation.

The justices took up the administration's appeal of a ruling against the policy by the New York-based 2nd US Circuit Court of Appeals in a case involving a Brazilian national. The Supreme Court will hear arguments in its new term, which begins on Monday, October 5, 2026.

The policy at the center of the dispute stems from guidance the US Department of Homeland Security issued in July 2025. That guidance told federal immigration officials that immigrants in the United States illegally are subject to mandatory detention without a bond hearing for the duration of their deportation proceedings — proceedings that can take months or even years to conclude.

The guidance broke from a nearly three-decade-old interpretation of federal law under which immigrants already living in the United States could be released on bond while they pursued their cases in immigration court.

Trump has enforced a sweeping immigration crackdown — among his top priorities — since returning to office last year. The Supreme Court, with its 6-3 conservative majority, has allowed a number of the administration's hardline immigration policies to take effect.

The policy has generated enormous litigation. Immigrants detained under it have filed tens of thousands of lawsuits seeking release. A Reuters analysis published in February found that hundreds of judges across the country had ruled more than 4,400 times that the administration had detained such immigrants unlawfully.

The 2nd Circuit decision arose from a challenge brought by Ricardo Aparecido Barbosa da Cunha, a Brazilian national who entered the United States illegally around 2004 or 2005 and has remained since then. Immigration officers arrested him in September 2025 while he was driving to work in Norwood, Massachusetts, and authorities initially denied him a bond hearing under the disputed policy. Court papers show he was released on bond at a later stage of his case.

Split among appellate courts

The litigation has produced a split among federal appellate courts. The New Orleans-based 5th US Circuit Court of Appeals sided with Trump in a 2-1 decision in February, reversing rulings that had led to the release of two Mexican men. US Circuit Judge Edith Jones wrote that decisions by prior administrations not to use mandatory detention, as Trump is doing, do not mean "they lacked the authority to do more."

Most federal appellate courts that have reviewed the policy have ruled against it. Decisions by the 2nd Circuit and the Cincinnati-based 6th US Circuit Court of Appeals prompted the administration's appeal to the Supreme Court.

The mandatory detention dispute is not the only major immigration case on the court's docket this term. On Tuesday, September 29, 2026, the justices let the administration resume, for now, swiftly deporting migrants to countries other than their own without offering them a chance to show the harms they may face there. Arguments in that case are scheduled for December.

For the millions of immigrants in the United States illegally, the stakes are direct: whether they can seek release on bond while their deportation cases proceed, or face detention for the entire length of proceedings that can stretch on for years. A ruling from the Supreme Court, expected by the end of the term in June 2027, will determine which interpretation of federal detention law applies nationwide.