Peter Navarro, a former trade adviser to President Donald Trump, has been convicted of contempt of Congress for refusing to co-operate with a probe into the 2021 US Capitol riot.
Prosecutors said Navarro acted “above the law” by ignoring a subpoena from a congressional investigation.
He faces up to a year in prison for each of the two contempt counts.
Another Trump ally, Steve Bannon, was convicted of similar charges last year and is free pending appeal.
Navarro, a former senior trade adviser, was served a subpoena by the US House of Representatives select committee in February 2022.
But he refused to hand over any emails or documents or appear to testify before the panel.
He had cited executive privilege, which allows certain White House communications to be kept under wraps.
The committee had hoped to question Navarro on efforts to delay certification of the 2020 election, according to a former staff director for the panel who testified in court.
Navarro was indicted in June 2022 and arrested by FBI agents at a Washington airport as he was boarding a flight to Nashville, Tennessee.
During a brief trial this week, prosecutors sought to portray the case as a relatively straightforward one with far-reaching implications.
“This case is all about a guy who didn’t provide documents. This case is just about a guy who didn’t show up for his testimony,” justice department prosecutor John Crabb said in his opening statement. “This case is that simple”.