A judge moves forward with a contempt of court investigation into the transfer of American immigrants to an El Salvador prison in March

A federal judge said Wednesday that he intends to move quickly on a contempt investigation of the Trump administration for failing to return planes carrying Venezuelan migrants to El Salvador in March.

US District Judge James Bosberg in Washington said that the ruling issued on Friday by the US Court of Appeals for the District of Columbia Circuit gave him the authority to proceed with the investigation, which will determine whether there is sufficient evidence to refer the matter to trial. He asked attorneys by Monday to identify witnesses and submit plans for how the investigation would be conducted, and said he would like to begin any hearings on Dec. 1.

The judge previously warned that he might seek to prosecute administration officials.

On March 15, Boasberg ordered the plane carrying the accused gang members to return to the United States, but it instead landed in El Salvador, where the migrants were being held in a notorious prison.

He watches: Former Venezuelan detainees speak out about abuses in El Salvador’s massive prison

“I have been authorized to proceed exactly as I intended to do in April seven months ago,” the judge said during a hearing Wednesday. He later added: “I certainly intend to find out what happened that day.”

Boasberg said having witnesses testify under oath seemed like the best way to conduct a contempt inquiry, but he also suggested the government make written declarations to clarify who had given the orders to “challenge” his rule. He suggested one witness: a former U.S. Justice Department lawyer who filed a whistleblower complaint alleging that a senior department official suggested the Trump administration might have to ignore court orders as it prepares to deport Venezuelan immigrants it accused of being gang members.

The Trump administration has denied any violation, saying the judge’s directions to return the planes were issued orally in court but were not included in his written order. Justice Department lawyer Tiberius Davis told Bosberg that the government objected to continuing the contempt proceedings.

Boasberg previously found probable cause to hold the Trump administration in criminal contempt of court. The ruling was a dramatic battle between the judicial and executive branches of government, but a divided three-judge appeals panel later sided with the administration and overturned the outcome. The two justices in the majority were appointed by President Donald Trump.

A larger panel of judges on the D.C. Circuit said Friday that their colleagues’ earlier ruling did not prevent Boasberg from moving forward with his contempt investigation. Judges Cornelia Bellard, Robert Wilkins and Bradley Garcia wrote that Boasberg’s contempt finding was a “thoughtful and substantive response.”

“Obedience to court orders is vital to the judiciary’s ability to fulfill its constitutionally defined role,” they wrote. “Injunctions are not suggestions, but rather binding orders that the executive, like any other party, must obey.”

The Trump administration invoked the 18th-century law of war to send the migrants, whom it accused of belonging to a Venezuelan cartel, to a massive prison in El Salvador known as the Center for Terrorism Confinement, or CECOT. She said that US courts could not order their release.

In June, Boasberg ruled that the Trump administration should give some migrants a chance to challenge their deportations, saying they could not formally contest the deportations or allegations that they are members of the Tren de Aragua.

The judge wrote that “significant evidence” had emerged indicating that many of the immigrants were not connected to the gang “and were therefore languishing in a foreign prison on flimsy, even frivolous, charges.”

More than 200 migrants were later released to Venezuela in a prisoner exchange deal with the United States

Their lawyers want Boasberg to issue another order asking the administration to explain how it will give at least 137 men a chance to challenge their gang designation under the Foreign Enemies Act.

Lee Gelernt, an attorney with the American Civil Liberties Union, said Wednesday that the men are in danger in Venezuela and afraid to talk to lawyers, who have been able to contact about 30 of them, but they “overwhelmingly” want to pursue their cases.

Davis said it may be difficult to detain the men again given tensions between the United States and the government of Venezuelan President Nicolas Maduro.

Boasberg did not immediately rule on the matter.