Manafort has a similar motion pending to dismiss criminal charges set for trial in July in federal court in Alexandria, Virginia. Manafort, 69, has pleaded not guilty in both cases and argued that Mueller exceeded his authority in charging him with felonies including conspiracy, bank and tax fraud, money laundering and failing to register as a lobbyist in his work before 2014 on behalf of Ukraine's pro-Russian president at the time, Viktor Yanukovych. Following the release of Jackson's opinion, Jason Maloni, a spokesman for Manafort, said, "Paul Manafort maintains his innocence and looks forward to prevailing in this matter." Manafort's attorneys have argued that Deputy Attorney General Rod Rosenstein acted improperly when he appointed Mueller in May 2017 to investigate not only collusion with Russia but any other issues that "may arise" from that investigation. They objected to Manafort being charged for alleged conduct that occurred before the 2016 campaign, and asserted that the authorisation for Mueller's probe was so broad it was a "blank check" and violates Justice Department regulations they say call for a "specific factual statement" of matters under investigation.

In her opinion, Jackson rejected those arguments. "It bears emphasising at this stage that Manafort is presumed to be innocent of these charges," she said, "But the indictment will not be dismissed, and the matter will proceed to trial." Paul Manafort in July 2016, as Trump campaign chairman Credit:AP Manafort, she wrote, "was, at one time, not merely 'associated with,' but the chairman of, the Presidential campaign, and his work on behalf of the Russia-backed Ukrainian political party and connections to other Russian figures are matters of public record." Jackson called it "logical and appropriate" for investigators tasked with probing for links between the Russian government and campaign associates "to direct their attention to him."

She wrote that "given the combination of his prominence within the campaign and his ties to Ukrainian officials supported by and operating out of Russia, as well as to Russian oligarchs, Manafort was an obvious person of interest." Rosenstein also had authority "to define the Special Counsel's charter broadly," and explicitly confirmed Mueller's authority to investigate Manafort's Ukrainian work in an August 2017 memo, she found. Loading Jackson said the regulations are not meant to allow investigation targets to use them to challenge criminal, but are intended to provide independence and accountability in sensitive investigations, giving a special counsel wide discretion while requiring department consultation and approval, which she said was done. "This is exactly what the Department of Justice regulations contemplate . . . The management of the investigation into the allegations against Manafort has been consistent with the objectives and requirements of the set of regulations as a whole, as well as the terms of the individual regulation upon which the defendant relies," said Jackson, a 2011 Obama appointee.

Deputy Solicitor General Michael Dreeben had defended the investigation, arguing last month in the District that prosecutors would naturally want to scrutinise Manafort's long-standing ties to Russian-backed politicians, financiers and others and whether any served as "back channels to Russia." Manafort joined the Trump campaign in March 2016 and resigned that August amid news reports about his activities in Ukraine. Manafort's indictment includes a conspiracy count citing alleged conduct going into 2016. Tuesday's opinion by Jackson was issued days after both sides argued a similar set of issues to dismiss charges before US District Judge T.S. Ellis III of Alexandria. Ellis, who has yet to issue an order, has asked to see an unredacted copy of the memo that lays out the special counsel's lines of investigation. In the Virginia courthouse, Ellis sharply questioned prosecutors about their motivations and whether they had exceeded their charging authority to pressure Manafort to turn against Trump or colleagues.

Ellis, a 1987 Reagan appointee, said the special counsel still may well have the authority to bring the charges, adding at one point, "I'm not saying it's illegitimate." But Ellis also suggested that if he ruled in Manafort's favor, the case could simply be returned to the US attorney's office for the Eastern District of Virginia. Washington Post