A federal judge on Friday tossed out former Trump campaign chairman Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE's lawsuit challenging the scope of 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 investigation.

In her decision, U.S. District Judge Amy Berman Jackson wrote that a civil suit is not the way for Manafort to challenge actions by the prosecutors who are working for Mueller's office.

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"A civil case is 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," wrote Berman Jackson, who was appointed by President Obama.

"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 defect in the prosecution in the trial court or on direct appeal.

"Therefore, the Court finds that this civil complaint must be dismissed."

Manafort filed the lawsuit in January, claiming that Mueller's investigation is overly broad and not permitted under Justice Department regulations.

“By ignoring the boundaries of the jurisdiction granted to the Special Counsel in the Appointment Order, Mr. Mueller acted beyond the scope of his authority. Mr. Mueller’s actions must be set aside,” a January court filing from Manafort's team said.

Manafort's lawyers argued that Mueller's appointment was illegal and that the charges against the former campaign chairman, which surround his lobbying work for pro-Russian political parties in Ukraine, fall outside the scope of Mueller's work.

A Department of Justice spokesman called Manafort's lawsuit "frivolous" after it was filed.

The former Trump aide is charged along with his business associate, Richard Gates, of hiding millions of dollars made from lobbying work in Ukraine from U.S. authorities. Gates pleaded guilty earlier this year.

Manafort has pleaded not guilty to the charges against him. His trial is set to begin in September.