A Senate committee chairman issued a subpoena this week to one of the spies the FBI used against Donald Trump's campaign before the 2016 campaign.
Stefan Halper, 76, was told to appear at the Dirksen Senate Office Building in Washington on Oct. 20.
Halper was told he would be answering questions about or related to Crossfire Hurricane, the FBI's counter-intelligence investigation of Trump's campaign; an investigation into that investigation by the Department of Justice's Office of Inspector General; and the unmasking of U.S. persons or entities affiliated, formally or informally, with the Trump campaign, the Trump transition team, or the Trump administration.
Halper faces penalties if he refuses to appear.
A spokesman for the committee didn't respond to a request for comment.
Neither Halper nor his lawyer responded to requests for comment.
Johnson and other Republicans have argued that the probe was rife with malfeasance, pointing to the reliance on an unsubstantial dossier that relied on Russians to make outlandish claims about Trump.
Democrats opposed the subpoenas and say Republicans should focus on combating the COVID-19 pandemic.
He was later brought back and got close to Carter Page, a Trump campaign adviser who was illegally spied on by the FBI, as well as George Papadopoulos, another aide.
Halper has not spoken publicly about his spying activities. According to publicly available information, he has not been questioned by Congress or the inspector general about his spying.
"What’s particularly terrible about it—and again, I talk about this in some length in my book—it’s the dual standards of justice, right? Where, well, we don’t want to leak anything related to Professor Halper, right? His name is not even in the 480-page Inspector General report, right? But nonetheless, there’s all kinds of false information about me," he said.