Special Counsel Robert Mueller's team is fighting a bid by a Russian firm to join an appeal brought by an American who is seeking to challenge the legitimacy of Mueller's appointment.

In a motion filed on Monday, the prosecutors argued that the court should not allow Concord Management and Consulting, LLC to "intervene" in the appellate case of Andrew Miller, a former associate of longtime Donald Trump friend and self-described political "dirty trickster" Roger Stone.Concord is the Russian firm that prosecutors say financed a St. Petersburg "troll factory" called the Internet Research Agency, which U.S. officials say set up hundreds of fake or automated social media accounts as part of a widespread online influence campaign ahead of the 2016 election. The firm has pleaded not guilty to a charge of conspiracy to commit fraud.

Miller served as an aide to Stone until 2013, according to Stone, who once described Miller as his "wingman" because he helped manage Stone's schedule, travel and media appearances, and also provided "some I.T. work." Miller identifies himself as a libertarian and has said he did not support Trump's candidacy, but he did accompany Stone to the 2016 Republican National Convention.

Miller turned over requested documents to prosecutors but was also subpoenaed to testify before a grand jury in the Russia probe in late June. After an unsuccessful attempt by his attorney last month to quash the subpoena to testify, Miller was held in contempt of court for refusing to comply with it.Andrew Miller, former aide to Roger Stone, seen here in this undated profile picture.

ABC News reported earlier this month that Miller's legal fight, now heading to the U.S. Court of Appeals, is being steered by a veteran Washington legal group that has a history of taking on Democrats and is bankrolled, in part, by longstanding Republican donors.

Attorneys for both Miller and Concord have argued that Mueller's appointment as special counsel was unconstitutional -- and both have lost those arguments in lower courts. Miller appealed his loss and, late last week, attorneys for Reed Smith, the American law firm representing Concord, moved to legally join in that appeal."Basic fairness therefore dictates that Concord should be permitted to participate in this appeal," Concord's motion said. Concord has also filed its own appeal, but said the "unique circumstances of this case," including the overlapping arguments against Mueller's appointment, should permit the firm to join in with Miller's.

Miller's legal team did not oppose the move. Paul Kamenar, Miller's attorney, told ABC News that "Concord has the better argument than the special counsel does that intervention should be granted" in Miller's appellate case. "I suspect the Court of Appeals will grant Concord's motion," Kamenar said, adding that the court's decision could come as soon as this week

A view of the four-story building known as the "troll factory" in St. Petersburg, Russia, Feb. 17, 2018. The U.S. government alleged the Internet Research Agency started interfering as early as 2014 in U.S. politics, extending to the 2016 presidential election, saying the agency was funded by a St. Petersburg businessman Yevgeny Prigozhin.

In its motion filed on Monday, prosecutors said that Concord should not be allowed to join Miller's appellate case because the firm "has not suffered a concrete and particularized injury as a result of the district court's contempt finding against Andrew Miller."

"In any event, the participation of Concord -- a defendant in a separate criminal case -- in this grand jury appeal is unwarranted," prosecutors said.

In a motion filed on Wednesday in response to the government, Concord argued that their "injury originates in the very same place as Mr. Miller's." Concord said Miller used its argument against Mueller's appointment in his original motions to quash the subpoena, and therefore Concord should be allowed to defend that argument before the appeals court, rather than rely on Miller's attorney to do so.

Concord, which prosecutors say is controlled by a close associate of Russian President Vladimir Putin, is one of three Russian entities, along with 13 Russian individuals, charged in connection with the alleged online influence operation, according to court documents. Concord is the only defendant to engage with the court through its U.S.-based attorneys.

Kamenar said he "obviously professionally" has been in communication with Concord's attorneys at Reed Smith and said that should the judge grant the intervening motion, he expects the two legal teams will be "in close communication." James Martin, an attorney at Reed Smith, declined to comment for this report.

Mitchell Epner, a former federal prosecutor who is now at the law firm Rottenberg Lipman Rich, said he's skeptical of Concord's chances for the intervening motion.

"It's not clear to me why they would be granted the right to intervene here when they have their own separate case where they could take their own, independent appeal to fully present their argument," he said.

ABC News, August 29,2018

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August 31, 201