A federal judge on Thursday prohibited the Trump administration from deporting any Venezuelans in South Texas under the 18th-century Alien Enemies Act.

U.S. District Judge Fernando Rodriguez Jr., a Trump appointee, became the first jurist to rule that the Act cannot be applied to individuals the administration asserts are gang members “invading” the United States.

“Neither the Court nor the parties question that the Executive Branch can direct the detention and removal of aliens who engage in criminal activity in the United States,” wrote Rodriguez, according to The Associated Press.

But, he said, “the President’s invocation of the AEA through the Proclamation exceeds the scope of the statute and is contrary to the plain, ordinary meaning of the statute’s terms.”

In March, President Trump issued a proclamation asserting that the Venezuelan gang Tren de Aragua was “invading” the United States and invoking special powers to deport those his administration labeled as gang members without standard court procedures.

“Allowing the President to unilaterally define the conditions when he may invoke the AEA, and then summarily declare that those conditions exist, would remove all limitations to the Executive Branch’s authority under the AEA, and would strip the courts of their traditional role of interpreting Congressional statutes to determine whether a government official has exceeded the statute’s scope,” the judge wrote. “The law does not support such a position.”

The Alien Enemies Act—a statute last used during World War II to authorize the internment of Japanese-Americans—had only been invoked three times prior.

That proclamation spurred a wave of litigation as the administration sought to send documented illegal alien gang members to a super-maximum security prison in El Salvador after the administration cut a deal with its government

Rodriguez’s ruling represents the first permanent injunction barring the administration from using the AEA in this manner, finding that the president has misapplied the law. But it’s a certainty that the administration will appeal.