A federal judge on Thursday told Stephen K. Bannon, a longtime adviser to former President Donald J. Trump, to surrender by July 1 to start serving a four-month prison term for disobeying a congressional subpoena.
Mr. Bannon was sentenced in October 2022 on contempt of Congress charges after he refused to give testimony to the House committee that investigated the Jan. 6, 2021, attack on the Capitol.
Judge Carl J. Nichols, who has overseen the case, allowed him to remain free while he appealed. Last month, however, Mr. Bannon lost the first round of that challenge as a three-judge panel of a federal appeals court in Washington decided that his guilty verdict on charges of ignoring the House committee’s demand for his testimony was proper.
Because of the panel’s ruling, Judge Nichols said he no longer believed that Mr. Bannon could rightfully continue to postpone serving his sentence.
“I do not feel my original basis for Mr. Bannon’s stay exists any longer,” he said.
Lawyers for Mr. Bannon have promised to ask the full appeals court to reconsider the panel’s decision. And Judge Nichols said that Mr. Bannon would have to start serving his sentence in less than four weeks unless the full appeals court took the case and issued its own ruling to pause the sentence from being enforced.
Judge Nichols’s decision seemed to catch Mr. Bannon’s lawyer, David Schoen, by surprise, and he approached the podium after it was issued and started arguing with the judge.
Judge Nichols dressed him down.
“One thing I think you need to learn as a lawyer is that when a judge has decided, you do not get up and yell at them,” the judge shot back.
During his brief trial two summers ago, Mr. Bannon was similarly defiant, contesting the charges that he had snubbed the House committee both inside and outside the courtroom. At one point, he delivered a speech promising to go “medieval” on the prosecutors who had brought the indictment against him.
After the hearing on Thursday, he remained recalcitrant, declaring that he would challenge his conviction all the way to the Supreme Court if necessary.
Speaking to reporters outside the courthouse, Mr. Bannon sought to portray the case against him as an attack on Mr. Trump and his supporters.
“This is about shutting down the MAGA movement, shutting down grass-roots conservatives, shutting down President Trump,” he said, adding, “There’s nothing that can shut me up.”
Mr. Bannon’s legal travails could continue after — or even during — his stint in prison.
A couple of months after he was found guilty of contempt of Congress in Washington, state prosecutors in Manhattan accused him of misusing money he helped raise for a group backing Mr. Trump’s border wall. In his final hours in office in 2021, Mr. Trump pardoned Mr. Bannon in a separate federal case that focused on similar accusations.
Mr. Bannon’s fraud trial is scheduled to take place later this year in the same Manhattan courthouse where Mr. Trump was recently convicted on charges of falsifying business records to cover up a sex scandal that threatened his 2016 run for the presidency.
Another former aide to Mr. Trump is already serving a prison term for refusing to take part in the House committee’s wide-ranging investigation into Mr. Trump’s efforts to remain in power after losing the 2020 election.
In March, Peter Navarro, who once worked as a trade adviser to Mr. Trump, reported to federal prison in Miami to begin serving his own four-month prison stint after a jury found him guilty of contempt of Congress for ignoring one of the committee’s subpoenas.