The city of Chicago was hit by a lawsuit on Wednesday by members of Black Lives Matter and other groups who are demanding federal oversight of police reforms. The lawsuit, filed after Mayor Rahm Emanuel appeared to backtrack on a promise to ensure federal oversight, asks the court to step in to ensure a halt to excessive force and alleged harassment of minorities. “Chicago has proven time and time again that it is incapable of ending its own regime of terror, brutality and discriminatory policing,” the lawsuit says. “Absent federal court supervision, nothing will improve.” Chicago police have been under increased scrutiny since an investigation by the Justice Department uncovered a pattern of excessive force by officers in January. Emanuel subsequently agreed to a court-ordered reform deal and took steps to overhaul the police department, but he announced earlier this month that he was considering using an independent monitor rather than court oversight.