A federal appeals court decided on Tuesday that the Trump administration is not allowed to hasten the deportation of alleged members of the Venezuelan gang Tren de Aragua using a historical wartime statute from the 18th century.

In a 2-1 verdict, the Fifth US Circuit Court of Appeals agreed with immigrant rights advocates and previous court rulings, asserting that the Alien Enemies Act of 1798 was not meant for addressing issues like those posed by the Tren de Aragua gang.

“The use of a wartime law during times of peace by the Trump administration to control immigration has been rightly invalidated by the court,” stated Lee Gelernt, representing the American Civil Liberties Union. “This significant decision curtails the administration’s inclination to declare emergencies without judicial scrutiny.”

The Alien Enemies Act has only been applied three times in the nation’s history, each instance during declared wars: the War of 1812 and the two World Wars.

The Trump administration contended that the courts should not question the president’s assessment that Tren de Aragua was affiliated with the Venezuelan government and posed a threat to the US, justifying the use of this law.

The administration took action by deporting members of Tren de Aragua to a large prison in El Salvador, where authorities argued that US courts had no jurisdiction to demand their release.

More than 250 of the deported migrants returned to Venezuela under a deal announced in July.

In a 2-1 ruling, the court granted the preliminary injunction sought by the plaintiffs because they “found no invasion or predatory incursion” in this case.

The court’s ruling blocks deportations from Texas, Louisiana and Mississippi.

The majority opinion said Trump’s allegations about Tren de Aragua do not meet the historical levels of national conflict that Congress intended for when the law was approved.

“A country encouraging its residents and citizens to enter this country illegally is not the modern-day equivalent of sending an armed, organized force to occupy, to disrupt, or to otherwise harm the United States,” US Circuit Judges Leslie Southwick and Irma Carrillo Ramirez wrote.

In a dissent, US Circuit Judge Andrew Oldham argued that the majority was second-guessing Trump’s conduct in foreign affairs and national security, which are areas where courts often give the president great deference.

“The majority’s approach to this case is not only unprecedented—it is contrary to more than 200 years of precedent,” Oldham wrote.

The Trump administration secured one legal victory in Tuesday’s ruling, with the judges finding the procedures officials use to advise detainees under the Alien Enemies Act about their legal rights are appropriate.

The ruling can be appealed to the full Fifth Circuit or directly to the US Supreme Court, which is expected to make the ultimate decision in this case.

The Associated Press contributed to this report.