The decision dealt a blow to a central part of the former Trump campaign chairman’s defense: that an investigation into his past lobbying work is beyond the scope of the special counsel’s mandate.
WASHINGTON — A federal judge on Friday dismissed a lawsuit filed by Paul Manafort, the former campaign chairman for President Trump, that tried to narrow the authority of the special counsel investigating Russian interference in the 2016 election.
The judge said that Mr. Manafort’s suit, which argued that the special counsel had exceeded his authorities by investigating Mr. Manafort’s past business dealings in Ukraine, was “not the appropriate vehicle for taking issue with what a prosecutor has done in the past or where he might be headed in the future.”
The ruling by the judge, Amy Berman Jackson, is a blow to a central part of Mr. Manafort’s defense strategy. The suit filed in January — taking direct aim at both Robert S. Mueller III, the special counsel, and Rod J. Rosenstein, the deputy attorney general who appointed him — argued that the charges against him are unrelated to Mr. Mueller’s primary task of investigating whether any of Mr. Trump’s associates assisted Russia’s campaign to disrupt the election.
Mr. Manafort is facing dozens of charges of money laundering, bank fraud, tax evasion and failing to register as a foreign agent in connection to work he did for years on behalf of Viktor F. Yanukovych, the former president of Ukraine who was an ally of President Vladimir V. Putin of Russia. Court documents say that Mr. Manafort used millions of dollars he received for the work to fund a lavish lifestyle filled with expensive homes, cars and designer suits.
Mr. Manafort has pleaded not guilty. Mr. Mueller has made public no evidence that Mr. Manafort coordinated with Russia’s attempts in 2016 to influence the American election.
Judge Jackson’s decision allows Mr. Mueller’s team to proceed with a planned trial against Mr. Manafort, expected to begin this year.
“It is a sound and well-established principle that a court should not exercise its equitable powers to interfere with or enjoin an ongoing criminal investigation when the defendant will have the opportunity to challenge any defects in the prosecution in the trial court or on direct appeal,” Judge Jackson wrote.
Mr. Manafort’s legal team is expected to appeal Judge Jackson’s ruling. A lawyer for Mr. Manafort, Kevin Downing, did not respond to a request for comment.
The claims in Mr. Manafort’s lawsuit echoed allegations made by Mr. Trump and his allies, that the special counsel’s team is on a partisan fishing expedition and has exceeded its original Justice Department mandate. Mr. Trump repeated this charge on Friday, calling the Russia investigation “a total Witch Hunt!”
“MUST END NOW!” he wrote on Twitter .
In his order last year that appointed Mr. Mueller, Mr. Rosenstein gave the special counsel power to investigate not only the issue of coordination between the Trump campaign and Russia but also “any matters that arose or may arise directly from the investigation.”
Mr. Manafort’s defense was dealt another blow in February when Rick Gates, his longtime business associate who joined him to work on the Trump campaign, pleaded guilty to financial fraud related to their work for Mr. Yanukovych. Mr. Gates is cooperating with the special counsel, potentially giving Mr. Mueller’s team a first-person account of the conduct Mr. Manafort is accused of in the indictments against him.
