In a significant Clean Water Act ruling, on March 4, 2025, the U.S. Supreme Court narrowed the Environmental Protection Agency’s (“EPA”) authority under the National Pollutant Discharge Elimination System (NPDES) permitting process. The decision in City and County of San Francisco v. Environmental Protection Agency, 604 U.S. ___, 145 S. Ct. 704 (2025) strikes down the EPA’s use of “end-result” provisions that held cities and entities responsible for the overall condition of receiving waters, regardless of their direct pollutant discharges.

Previously, the EPA could require permit holders to meet broad water quality standards—essentially holding them accountable for the health of rivers, lakes, or oceans affected by runoff and discharge. The Court ruled that these requirements overstepped the agency’s statutory authority under the Clean Water Act.

The Court upheld the EPA’s power to impose specific, measurable effluent limitations—standards based on pollution control technology—to limit pollutant levels in discharges. When these technology-based limitations fall short, water quality-based limits are still available to regulators, as long as the limits are tied to the discharger’s actual output.

This ruling is likely to shift how municipalities and regulated parties are held accountable for water quality, potentially easing compliance burdens, but raising new concerns about environmental oversight. The EPA may issue new permitting guidance as it recalibrates its approach to pollutant discharges into waters protected under the Clean Water Act, which may in turn be met with further litigation by dischargers.