Federal Reserve board of governors member Lisa Cook sued President Trump on Thursday over his "unprecedented and illegal attempt” to remove her from her position. 

She asked a judge to block her removal from the board to “safeguard” its congressionally mandated independence, allowing her and the Fed at large to “continue its critical work.” 

“The operational independence of the Federal Reserve is vital to its ability to make sound economic decisions, free from the political pressures of an election cycle,” the complaint reads.

The lawsuit also names Federal Reserve Chair Jerome Powell and the board of governors as defendants. 

The Federal Reserve Act says the president can only remove members of the governing board “for cause.” The courts have never weighed exactly what that means because no president has sought to remove a Fed governor, until now.  

Trump claimed in his Monday letter firing Cook that he does have cause to remove her, pointing to a criminal referral from the Federal Housing Finance Agency that suggests she may have made false statements on one or more mortgage agreements. 

The referral alleges Cook illegally deemed two properties in Michigan and Georgia her “primary residence,” a declaration that can result in a lower interest rate.  

“The American people must be able to have full confidence in the honesty of members entrusted with setting policy and overseeing the Federal Reserve,” Trump wrote. “In light of your deceitful and potentially criminal conduct in a financial matter, they cannot and I do not have such confidence in your integrity.” 

In the lawsuit, Cook claims the allegations do not meet the legal requirements to remove her.

To let her firing stand would “subvert the Federal Reserve Act, which explicitly requires a showing of ‘cause’ for a Governor’s removal, which an unsubstantiated allegation about private mortgage applications submitted by Governor Cook prior to her Senate confirmation is not,” the complaint reads.  

The Fed declined to comment. The Hill requested comment from the White House and Cook's legal team.

Updated at 10:05 a.m. EDT