The Equal Employment Opportunity Commission doesn’t have authority to sue employers over sweeping job patterns or practices that allegedly lead to workplace bias without first going through procedural steps laid out by federal law, the agency said in an opinion letter released Thursday.

The agency said a worker must file a discrimination charge with the agency, and attempt to resolve the dispute through conciliation, before the EEOC can bring a “pattern or practice” suit against an employer under Section 707 of Title VII of the Civil Rights Act of 1964.

The opinion letter comes one week after the agency held a closed meeting to discuss its Section 707 power. It reverses interpretations previously used by the agency to bring systemic discrimination cases against companies. The agency has brought such suits in the past without adhering to those requirements, drawing a rebuke from the U.S. Court of Appeals for the Seventh Circuit in a 2015 case involving CVS Pharmacy.