On May 9, 2023, the U.S. Court of Appeals for the D.C. Circuit held that the Environmental Protection Agency’s (EPA’s) decision not to regulate perchlorate in drinking water violated the Safe Drinking Water Act (NRDC v. Michael Regan, et al., USCA Case #20-1335). When perchlorate is ingested through drinking water, it can disrupt thyroid hormone production, leading to neurodevelopmental issues, particularly in fetuses and young children. Due to these risks, in 2011 the EPA issued a final determination to regulate perchlorate in drinking water nationally. However, the EPA never promulgated such regulations and withdrew its own determination that it should regulate perchlorate. The National Resources Defense Council (NRDC) petitioned for review, arguing that the EPA lacked the authority to withdraw that determination under the Safe Drinking Water Act.

A Wilson Sonsini pro bono team submitted an amicus brief on behalf of 14 leading scientists, public health professionals, and researchers in support of the NRDC’s petitions for review. In this latest decision, the D.C. Circuit panel held that the Safe Drinking Water Act does not permit the EPA to withdraw a regulatory determination and granted the NRDC’s petition. EPA’s withdrawal decision was vacated and remanded to the agency for further proceedings. The decision represents an important victory regarding agency action and the EPA’s duty to promulgate national standards for clean drinking water.

The Wilson Sonsini team that worked on the matter was led by partners David Berger and Deno Himonas and included John Peterson, Larissa Lee, Lisa Davis, Anthony Geritano, and Diana Lopez.