A federal appeals court in Washington has upheld the validity of special counsel Robert Mueller III’s appointment, marking the first time a federal appeals court has affirmed the investigation that’s netted dozens of indictments and several convictions.

A three-judge panel for the U.S. Court of Appeals for the D.C. Circuit unanimously rejected on Tuesday one man’s long-shot bid to challenge Mueller’s appointment. Andrew Miller, an ex-assistant to Roger Stone, a longtime Trump ally who was recently indicted in the special counsel probe, brought the appeal after a lower court held him in contempt for resisting grand jury subpoenas issued last year by Mueller’s prosecutors.