The court hears arguments Sept. 29 on whether Boasberg may keep investigating who defied his order to turn deportation flights around. The department wants the inquiry shut down entirely, the brief said.
Boasberg has served on the federal bench in Washington since 2011, when President Barack Obama appointed him, according to the Federal Judicial Center. President George W. Bush had named him to the D.C. Superior Court in 2002.
The order at the heart of the fight requires two department lawyers to testify under oath about the flights, a step the department says would expose confidential legal advice.
Fired Justice Department attorney Erez Reuveni and Deputy Assistant Attorney General Drew Ensign were both directed to take the stand and answer questions from lawyers representing the deported migrants, the Associated Press reported.
"But Plaintiffs fail to identify any precedent for such an anomalous proceeding, which poses a mortal threat to the attorney-client privilege," the department wrote. "Yet the judge intends to put them on the stand and to allow opposing counsel to cross-examine them. That is grossly improper."
The filing went further, telling the appeals court that Boasberg has abandoned the role of a judge by running a criminal investigation himself.
"Plaintiffs' brief underscores the error of the district court's freewheeling criminal investigation into the mens rea of senior Executive Branch officers," the department wrote, using the legal term for a person's state of mind.
"Certainly they do not justify the unconstitutional, intrusive, and rapidly metastasizing pre-referral investigation the district court has launched," the brief said.
Department lawyers compared the planned hearing to a grand jury proceeding and leaned on a Seventh Circuit ruling that shut down a similar judicial inquiry, the filing said.
"Our legal system does not contemplate an inquisitorial role for federal judges," that court held, in a passage the department quoted.
The people who could face charges include Justice Department officials, not only the Homeland Security officials who carried out the flights. Lawyers for the migrants named Ensign and Emil Bove, now a federal appeals judge, as possible witnesses, and the department's own timeline added Acting Attorney General Todd Blanche and Kristi Noem, who was Homeland Security secretary at the time, Law Dork reported.
Sens. Sheldon Whitehouse (D-RI) and Richard Blumenthal (D-CT) described the matter the same way, calling it an investigation of "Emil Bove and other Department of Justice lawyers' potential contempt of court" in a 2025 letter to the appeals court's chief judge.
Blanche accused Boasberg of targeting Justice Department attorneys after an appeals panel blocked the inquiry in April, Fox News reported.
Bove now sits on the U.S. Court of Appeals for the Third Circuit. Reuveni alleged in a whistleblower complaint that Bove, then a senior Justice Department official, suggested the department might need to tell the courts "f— you" and press ahead with the removals anyway, according to former federal prosecutor Joyce Vance.
Bove later denied making the remark under oath at his Senate confirmation hearing.
The dispute began in March 2025. Boasberg ordered the government from the bench to turn around planes carrying Venezuelan men to a prison in El Salvador, and the flights continued anyway, according to a Lex Machina Review timeline.
His written order, entered after the hearing, barred future removals without spelling out any duty to bring back planes already in the air, the timeline said. The temporary restraining order covered 137 Venezuelans removed under the Alien Enemies Act, while public accounts of the three flights described more than 260 passengers.
Noem personally decided to proceed with the transfer of custody, the department told the appeals court.
The department argues the entire inquiry is pointless because no crime is possible. Its position is that "removing" in the order applied only to taking people out of U.S. territory, not to handing over custody of people already outside the country, the brief said.
Three judges on the D.C. Circuit — Gregory Katsas, Neomi Rao and Justin Walker — have already endorsed that reading, the department said.
"In short, given the considered views of three members of this Court, as well as the text and context of the TRO, no reasonable prosecutor would seek criminal-contempt charges in these circumstances, and no court could plausibly sustain them," the brief said.
The department also says the order was void from the start. The Supreme Court threw it out for lack of jurisdiction, and an order a court had no power to issue cannot support a contempt charge, the filing said.
Boasberg found probable cause in April 2025 to believe the government committed criminal contempt, the Lex Machina timeline said. Appeals panels blocked his discovery in August and ordered him to end the inquiry in April, before the full circuit wiped out that ruling on June 22.
More than 200 former federal and state judges have lined up against the department, calling Boasberg's investigative authority "uncontroversial" in a friend-of-the-court brief that points to three episodes in American history, Law and Crime reported.
"A court that issues orders a litigant is free to disregard or circumvent is not a court in any meaningful sense; it is instead an advisory body, and its judgments are mere suggestions," the former judges wrote, in a passage Vance quoted.
The department also asked the appeals court, if it rules against the government, to freeze the case for 14 days so the solicitor general can take the fight to the Supreme Court, the brief said.
