The Trump administration will not be allowed to deport a group of Venezuelan detainees accused of being members of a violent gang under a rarely invoked wartime law while the matter is litigated in the courts, the Supreme Court said on Friday.

The justices sent the case back to a federal appeals court, directing it to examine claims by the migrants that they could not be legally deported under the Alien Enemies Act, the centuries-old wartime law invoked by the Trump administration. The justices said the appeals court should also examine what kind of notice the government should be required to provide that would allow migrants the opportunity to challenge their deportations.

The court said its order would remain in place until the U.S. Court of Appeals for the Fifth Circuit ruled and the Supreme Court considered any appeal from that ruling.

Justice Samuel A. Alito Jr. wrote a dissent, arguing that the justices had no authority to hear the dispute at this stage. He was joined by Justice Clarence Thomas.

The ruling deals a sharp blow to the Trump administration’s efforts to deploy the wartime law to pursue swift, sweeping deportations of Venezuelan migrants accused of being members of the gang, Tren de Aragua.

It also suggests that a majority of the justices may be skeptical of whether the migrants have been afforded enough due process protections by the administration before being deported, potentially to a prison for terrorists in El Salvador.