(CNN) A federal district judge who was appointed by President Donald Trump has upheld Robert Mueller's appointment and constitutional authority in the special counsel's case against Russian social media propagandists.

Judge Dabney Friedrich, who serves at the trial-court level in DC federal court, said Concord Management and Consulting could not have its case tossed on constitutional grounds. The Russian company accused of backing a social media effort to sway voters against Democratic presidential candidate Hillary Clinton claimed Mueller didn't have power to bring the case because he was not appointment by the President and confirmed by Congress. Mueller was appointed under the authority of Deputy Attorney General Rod Rosenstein, who has broad power as the acting head of the Justice Department for the 2016 election probe.

"The appointment does not violate core separation-of-powers principles. Nor has the Special Counsel exceeded his authority under the appointment order by investigating and prosecuting Concord," Friedrich wrote in an opinion published Monday morning. She was one of the first judges Trump placed into a federal court position.

Friedrich cited opinions by three other federal judges -- Amy Berman Jackson, who oversees Paul Manafort's criminal foreign lobbying case; T.S. Ellis, who oversees Manafort's financial fraud case; and DC District Court Chief Judge Beryl Howell -- to back up her decision.

All three judges also denied requests to invalidate Mueller's authority, with Howell writing as recently as late July that a witness subpoenaed to turn over documents and to testify before the grand jury about Roger Stone would have to. That witness, Andrew Miller, has been held in contempt of the court and now may appeal.

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