A federal judge has ordered an associate of former Trump campaign adviser Roger Stone Roger Jason StoneThe agony of justice Our Constitution is under attack by Attorney General William Barr Justice IG investigating Stone sentencing: report MORE to testify before special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s grand jury.

U.S. District Court for the District of Columbia Chief Judge Beryl Howell rejected former Stone associate Andrew Miller’s attempt to challenge a subpoena for his testimony and documents in the probe.

CNN reported on the July 31 ruling, which shot down Miller’s argument that Mueller’s appointment as special counsel was unconstitutional.

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"Multiple statutes authorize the Special Counsel's appointment, and the official who appointed the Special Counsel had power to do so,” Howell wrote in her decision to deny Miller’s request on the subpoenas.

She ordered Miller to testify "at the earliest date available to the grand jury, and to complete production of the subpoenaed records promptly."

One of Miller’s attorneys, Paul Kamenar, told CNN that they are “obviously disappointed” in the decision and exploring their options in appealing the ruling.

Miller is one of several Stone associates recently subpoenaed in Mueller’s probe.

Mueller’s recent indictment against Russian intelligence officers for the 2016 hacking of the Democratic National Committee appeared to reference Stone. Stone, who is not facing charges in the probe, said that he is “probably” the unnamed individual referenced in the document.

Stone also revealed in June that he had met with a Russian man during the 2016 campaign, who had offered dirt on Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE in exchange for $2 million from then-candidate Donald Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE. Stone said he rejected the proposal.