Roger Stone appeared in court ahead of his trial on charges of witness tampering, obstruction and lying.

The longtime associate of President Donald Trump has challenged his prosecution as part of special counsel Robert Mueller’s probe, which accused him of lying to Congress about the 2016 campaign’s use of emails stolen by Russian hackers and dumped online by WikiLeaks.

Stone’s attorneys argued Thursday morning in federal court that lying charges should be thrown out because Congress did not make a formal criminal referral, reported Zoe Tillman of BuzzFeed News.

Judge Amy Berman Jackson, who Stone’s attorneys have tried to get removed from the case, asked defense attorneys for a legal authority to back their claims, but attorney Robert Buschel admitted he couldn’t find a specific case to support his argument.

Jackson told Stone’s attorney’s she didn’t understand their claims about separation of powers when Congress doesn’t require a criminal referral to prosecute someone for lying to lawmakers, and then the defense arguments fell apart.

The judge pointed out that former House Intelligence Committee chairman and Trump ally Devin Nunes (R-CA) had given the special counsel the entire Stone transcript with “no restrictions,” but Buschel insisted that didn’t give Mueller the authority to indict on perjury before Congress.

But Jackson was unmoved by his argument: “They gave it to a prosecutor.”