On Tuesday, March 4, 2025, the Supreme Court issued an opinion in City and County of San Francisco, California v. Environmental Protection Agency, U.S. No. 23-753 in which the City and County of San Francisco (San Francisco) challenged certain provisions in the Clean Water Act (CWA) National Pollution Discharge Elimination System (NPDES) permit for its Oceanside wastewater treatment plant (WWTP) that conditioned compliance on whether the receiving water body met certain water quality standards. Among other requirements and restrictions, the NPDES permit at issue prohibited the WWTP from 1) making any discharge that “contribute[s] to a violation of any applicable water quality standard,” and 2) performing any treatment or making any discharge that “create[s] pollution, contamination, or nuisance as defined by California Water Code section 13050.”

According to San Francisco, these permit requirements created significant uncertainty for the compliance status of its Oceanside WWTP by holding petitioner responsible for a condition it could not directly control—the quality of the oceanwater into which the WWTP discharges. The EPA, on the other hand, argued that it needs the authority to impose these “end-result” permit requirements when the regulated entity does not provide the agency with adequate information to craft more specific requirements that will be adequately protective of receiving water quality.

Justice Samuel Alito delivered the opinion of the Court, which held in a 5-4 opinion that the CWA provisions authorizing the EPA to impose “effluent limitations” (33 U.S.C. § 1311) in NPDES permits do not authorize such “end-result” requirements that “condition [permittees’] compliance on whether receiving waters meet applicable water quality standards.” In other words, the EPA cannot impose requirements that “simply tell[] a permittee that a particular end result must be achieved and that it is up to the permittee to figure out what it should do.” Justice Amy Coney Barrett, joined by three justices (Sotomayor, Kagan and Jackson), argued in dissent that there is nothing in the “straightforward statutory language” of the CWA that distinguishes “end-result” permit requirements from other requirements the majority found to be acceptable.

A driving concern for the majority was the potential hole that “end-result” requirements could create in CWA Section 1342(k), which deems a permittee to be in compliance with the CWA if it is in compliance with its permit. This “permit shield” provision offers certain legal assurances to permittees that would otherwise be exposed to harsh civil and even criminal penalties for violations of the CWA that are ultimately outside of their control. The Court found that “end-result” permit requirements, by “making the permittee responsible for any drop in water quality below the acceptable standard,” would potentially swallow the protections offered by Section 1342(k) and result in significant civil and criminal exposure for permittees, even when they comply with all the other terms of their permits.

A second key issue for the Court was the lack of any mechanism in the CWA for apportioning liability where multiple permittees, each with “end-result” permit requirements, discharge into the same water body. In such a case, the EPA would have to “unscramble the polluted eggs after the fact” to determine which permittee was liable. According to the Court, it was exactly this backwards-looking convoluted enforcement scheme that Congress sought to abandon when it amended the Water Pollution Control Act in 1972 to create the modern Clean Water Act.

Notably, the Court upheld “narrative” permit terms, such as requirements to implement best management practices without specifying the exact practices to implement in every given situation. In doing so, the Court rejected San Francisco’s argument that “all limitations” imposed under CWA Section 1311 must qualify as “effluent limitations” and upheld conditions that “do not directly restrict the quantities, rates, or concentration” of pollutants that a permittee may discharge.

The Court’s holding impacts NPDES permits throughout California and across the country. “End-result” permit requirements in the form of receiving water limitations are commonly found in general NPDES permits, including California’s Construction General Permit and Industrial General Permit, as well as site-specific NPDES permits. The Court’s holding also may impact pending regulatory and citizen-suit enforcement actions, at least to the extent such actions are based on “end-result” permit requirements similar to the ones rejected by the Supreme Court.