On Friday afternoon, the Supreme Court issued an emphatic and unusual decision declaring that the Trump administration violated the due process rights of Venezuelan migrants in its attempt to deport them to a Salvadoran prison. The government’s late-night race to expel these individuals, the court held, “surely does not pass muster” under the Constitution, failing to provide them with fair notice and an opportunity to contest their removal. The court also extended an injunction to stop the government from deporting an entire class of migrants under the Alien Enemies Act of 1798 while the case works its way through the lower courts. Only Justice Samuel Alito, joined by Justice Clarence Thomas, noted dissent.

In all, the ruling marks an astonishing defeat for the Trump administration. The court did not decide whether the president can, in fact, wield the Alien Enemies Act to banish migrants to a foreign prison. But it imposed vital constitutional safeguards on his efforts to do so, protecting more innocent people from unlawful expulsion and imprisonment overseas. And the court did all this on an exceptionally expedited basis, with minimal briefing and no argument. For the majority, it was not a close call: The government’s attempt to disappear migrants to a foreign black site is egregiously unconstitutional.

Friday’s ruling is a follow-up to the Supreme Court’s intervention, last month, in the Trump administration’s ongoing scheme to summarily deport migrants to CECOT, a brutal El Salvador prison. In March, the president invoked the Alien Enemies Act—an 18th-century wartime law that applies to invading armies—to justify rushing these individuals out of the country outside of usual immigration procedures. He accused them, without evidence, of belonging to a Venezuelan gang, which he deemed to be a “foreign terrorist organization.” The government first expelled more than 200 men to CECOT in March, in apparent violation of a district court order. Credible evidence showed that it was preparing to do the same on April 18 in the Northern District of Texas. When lower courts refused to step in, the migrants’ lawyers asked the Supreme Court for emergency aid. It obliged, issuing a one-paragraph order just before 1 a.m. halting the deportations.

In its new, unsigned decision—which was released without warning—the court explained and expanded its dramatic order last month. Immigrants, it noted, are entitled “to due process of law in the context of removal proceedings,” a fact that the court unanimously affirmed in a related case six weeks ago. So, under the Fifth Amendment, “no person shall be removed from the United States without opportunity, at some time, to be heard.” Here, the majority held, at a minimum, that migrants “must have sufficient time and information to reasonably be able to contact counsel, file a petition, and pursue appropriate relief.” It noted pointedly that, in the case of Kilmar Abrego Garcia, the government has claimed that it has no authority to retrieve migrants who’ve been sent to CECOT, and that federal courts have no jurisdiction to order their return. Migrants’ interests in a robust due process, the majority wrote, “are accordingly particularly weighty.”