St. Louis Circuit Attorney Kim Gardner has sued the city in federal court for what she says is a wide-ranging conspiracy against her efforts to address racial injustice. 

Citing the Ku Klux Klan Act of 1871, Gardner filed the federal lawsuit on Monday and listed the city's government, police union and multiple officials as defendants in the case. 

After her election win in 2016, Gardner says she faced an unprecedented and coordinated effort by white government officials to limit her effectiveness and to stop her from taking steps to remedy the city's "historical inequality."

"The United States Congress adopted the Ku Klux Klan Act … to address precisely this scenario: a racially-motivated conspiracy to deny the civil rights of racial minorities by obstructing a government official's efforts to ensure equal justice under law for all. The stakes are high. This case cries out for federal enforcement," she wrote in the lawsuit.

Top Black prosecutors from across the country came to St. Louis this week to rally behind Gardner's efforts to push through criminal justice reform and said they too had faced massive pushback from local police unions who fought any attempts to hold police accountable for crimes they commit.

"This is not about a single case or issue. This is about the fair administration of justice," she told CBS This Morning on Tuesday. The lawsuit says the police union and city officials attempted to "intimidate, silence, and sideline" her as she took meaningful steps to deal with racism in the police ranks.

The city has extraordinarily high rates of traffic stops, with the overwhelming majority being of the city's Black residents. St. Louis Police Department officers were featured prominently in a groundbreaking report on racist Facebook posts released last year from national research group the Plain View Project.

Dozens of officers were implicated in making hundreds of anti-Black and anti-Muslim Facebook posts, so Gardner added some of them to a list of police officials banned from bringing cases to her office. Two officers were later fired from the department for their Facebook posts.

But Garner's decision enraged the police union, and Jeffrey Roorda, a business manager for the St. Louis Police Officer's Association, has released a number of alarming statements, calling the lawsuit "a grand distraction."

"When she got elected to office she decided that she wanted to persecute cops instead of prosecuting criminals," Roorda told NBC affiliate KSDK on Monday.

The dispute between Gardner and the police union escalated when both sides decided to conduct their own investigations into Republican Gov. Eric Greitens, who was forced to resign amid sexual misconduct allegations.

The police union included Gardner in their own investigation, even though she was never charged with any crimes. Gardner was critical of the police union investigation because it was led by a man who is a lifelong friend of Greitens' lead lawyer.

The anti-Klan act that Gardner cites in her lawsuit was part of a wave of laws passed after the Civil War to stop white supremacists from infringing on the rights of Black people.

"You are not alone. We will not stand idly by any longer while the keepers of the status quo try to tear you down," said Baltimore state's attorney Marilyn Mosby during a protest on Wednesday.