A deeply divided Supreme Court on Monday afternoon shut down a federal judge’s efforts to stop the Trump Administration from secretly deporting foreign nationals under an 18th Century wartime enemies law, but ruled unanimously that anyone facing that threat from now on must first get a chance to pursue a court challenge.

By a vote of 5-to-4, in the most significant action the Court has taken so far on a variety of constitutional controversies stirred up by President Trump early in his second term, the Court ruled that individuals facing forced transfer to a foreign prison under the 1798 law must pursue their cases one at a time, rather than as a group of all those potentially at risk of sudden deportation. That will make challenges harder and slow down the legal process significantly.

The Court issued that ruling a short time after Chief Justice John G. Roberts, Jr., acting alone, put temporarily on hold another lower court’s order telling the Administration to take steps to bring back to the U.S. a Maryland resident who is a native of El Salvador who was sent to the prison there by mistake; a court had barred his being sent to El Salvador. The full Court may take action on that separate dispute soon, perhaps tomorrow.

Although President Trump and his aides have taken scores of controversial actions as they pursue a sharp turn away from normal government operations, the presidential team has claimed the greatest power in its campaign to swiftly deport perhaps millions of foreign nationals living in the U.S. The core argument has been that the President has unchecked power to do that, and that the courts may not interfere in any way. Both developments at the Court Monday involved such claims; those claims failed on Monday.

In the most decisive of Monday’s actions, the Court’s five-Justice majority did this:
• It stopped any further action in a federal trial court in Washington, D.C., on challenges to deportation by a broad group of Venezuelan nationals who the Administration intends to deport to El Salvador to be held at an infamous prison known for its brutality.
• It said that the group legal action in Washington is forbidden by federal law, so those foreign nationals must take their cases individually to a federal court in the locations where they are currently being held by the government – southern Texas, for most of them.
• Before any of those individuals may be deported, the government must give them advance notice and give them enough time to file their own, separate court cases where they are now held. They must be allowed to pursue their claim that the 1798 law can be used constitutionally only during wartime rather than in the current peacetime, and their claim that they are not members of a violent Venezuelan gang, as the government contends.  (The Court was unanimous on this point.)
• Those rights to notice and to make a challenge apparently will only apply to foreign nationals in the U.S. who remain here now, and thus does not appear to apply to anyone in the group of Venezuelans who has already been deported.
• Although the Washington judge so far had issued only temporary orders halting some of the deportations and questioning whether the Administration had violated those orders intentionally, temporary orders of a kind that usually cannot be challenged on appeal, the Court majority treated them as final orders open to appeal, and struck them down because they came in the wrong court under the wrong process.

The Court majority’s unsigned, four-page order did not settle the legality or constitutionality of using that old law for deportations at this time in history, and did not resolve whether it would be legal to deport any of the Venezuelans now facing that threat. Those issues could return to the Supreme Court after lower courts act.

The ruling had the tone of a compromise ruling, agreeing with the Administration that the Venezuelans had sued in the wrong court under the wrong legal process, while agreeing with lawyers for the foreign nationals that they had a constitutional right to be told of the threat of deportation and a right to contest the legality of their removal – to anywhere in the world, and specifically to a notorious prison in El Salvador.

The Court did not list the Justices who supported that order, but since it would take five votes to adopt the ruling, it was clear that it had the support of Chief Justice Roberts and of Justices Brett M. Kavanaugh (who wrote a brief separate opinion for himself), Joseph A. Alito, Jr., Neil M. Gorsuch and Clarence Thomas.

The four Justices who opposed all or at least key parts of the ruling did so in a 17-page dissenting opinion by Justice Sonia Sotomayor. That was joined in full by Justices Elena Kagan and Ketanji Brown Jackson, and joined in part by Justice Amy Coney Barrett. Justice Jackson also wrote a brief, separate opinion for herself.

While three of those dissenting Justices objected to all parts of the majority ruling, and leveled harsh criticism at the majority, Justice Barrett apparently joined only the dissent’s objection to directing the Venezuelans’ cases to individual future processes. She appeared to agree with the majority that the Washington judge’s temporary orders could be reviewed by the Supreme Court at this stage.

All nine Justices agreed with the ruling that the foreign nationals had a right to notice of the threat of deportation and a right to challenge their removal, perhaps on a wide variety of legal and constitutional theories. The ultimate fate of those challenges may not be known for a considerable period of time.