A federal appeals court in Washington, D.C., on Friday upheld criminal contempt charges against Steve Bannon, the one-time adviser to former President Donald Trump, for failing to comply with a subpoena to appear before the House committee investigating the Jan. 6, 2021, attack on the U.S. Capitol, according to reports.

The unanimous ruling from the three-judge panel means that Bannon will likely have to serve the four months sentence he received after being found guilty of two counts of contempt of Congress in 2022, CNBC reported. Bannon was allowed to remain free while he appealed the conviction.

Bannon claimed that he couldn't testify becaus he was bound by executive privilege not to divulge communicatins he had with then-President Donald Trump. 

The D.C. Circuit Court of Appeals said Bannon had no legal reason to refuse the subpoena. 

"Because we have no basis to depart from that binding precedent, and because none of Bannon's other challenges to his convictions have merit, we affirm [the conviction]," the judges said in the 20-page ruling, according to Politico.

"It is undisputed that the first time Bannon raised these arguments was in district court, long after his deadline for responding to the subpoena had passed," Judge Brad Garcia wrote, according to the Hill. 

"A witness cannot defend against a contempt of Congress charge based on an affirmative defense that they were able, but failed, to raise at the time they were ordered to produce documents or appear," Garcia said. 

Bannon, the host of a right-wing podcast, War Room, and another Trump White House adviser, Peter Navarro, defied their subpoenas to testify and turn over documents to the now disbanded committee. 

Navarro reported to federal prison in March to serve out his four-month sentence.