WASHINGTON (AP) A federal judge on Wednesday said he has found probable cause to hold the Trump administration in criminal contempt of court for violating his orders to turn around planes carrying deportees to El Salvador.

U.S. District Judge James E. Boasberg warned he could refer the matter for prosecution if the administration does not “purge” its contempt. Boasberg said the administration could do so by returning to U.S. custody those who were sent to the El Salvador prison in violation of his order so that they “might avail themselves of their right to challenge their removability.”

If the Justice Department declines to prosecute the matter, Boasberg said he will appoint another attorney to prosecute the contempt.

“The Constitution does not tolerate willful disobedience of judicial orders especially by officials of a coordinate branch who have sworn an oath to uphold it,” Boasberg wrote.

It marks an escalation in a battle between the judicial and executives branches of government over a president’s powers to carry out key White House priorities. The Republican president has called for Boasberg’s impeachment while the Justice Department has accused the judge of overstepping his authority.

Boasberg, who was nominated to the federal bench by Democratic President Barack Obama, ordered the administration last month not to deport anyone in its custody under the Alien Enemies Act. Trump invoked the 1798 wartime law over what he claimed was an invasion by the Venezuelan gang Tren de Aragua.

When Boasberg was told there were already planes in the air headed to El Salvador, which has agreed to house deported migrants in a notorious prison, the judge said the aircraft needed to be returned to the United States. But hours later, El Salvador’s president, Nayib Bukele, announced that the deportees had arrived in his country. In a social media post, he said, “Oopsie…too late” above an article referencing Boasberg’s order.

The Trump administration has argued it did not violate any orders, noted the judge did not include the turnaround directive in his written order and said the planes had already left the U.S. by the time that order came down.