– Special Counsel Robert Mueller defended his authority to prosecute Donald Trump’s former campaign chairman, Paul Manafort, and argued in court papers that Manafort improperly wants to use a lawsuit to secure dismissal of his money-laundering indictment.

Mueller’s prosecutors urged a judge to dismiss a lawsuit attacking the Oct. 27 indictment charging that Manafort did not register as an agent of the Ukrainian government and laundered millions of dollars before he worked on Trump’s presidential campaign.

“The special counsel’s investigation and prosecutions are entirely lawful,” prosecutors argued in a motion filed late Friday. “If Manafort believes the special counsel lacks authority to prosecute him, he is free to raise that objection in his criminal action by filing a motion to dismiss the indictment.”

Manafort filed the lawsuit Jan. 3 after weeks of mounting assaults by many Republican lawmakers and conservative media of Mueller and members of his team, attacking them as unfair and biased.

The filing by Mueller’s prosecutors came after the release of a memo by Republicans on the House Intelligence Committee alleging bias by FBI and Justice Department officials involved in the investigation into Trump and Russia in 2016.

In the lawsuit, Manafort’s lawyers claim that Mueller overstepped his mandate to pursue “any matters that arose or may arise directly from the investigation” into Russian meddling in the 2016 election. Manafort claimed that Mueller’s team improperly interpreted its authority as “carte blanche” to pursue crimes beyond Russian collusion.

In the filing, prosecutors cited the Dec. 13 congressional testimony of Deputy Attorney General Rod Rosenstein, who oversees Mueller’s work because Attorney General Jeff Sessions recused himself.

“I’m properly exercising my oversight responsibilities, and so I can assure you that the special counsel is conducting himself consistently with our understanding” about the probe’s scope, he said. A copy of his testimony was attached.