On May 29, 2025, the U.S. Supreme Court issued an 8-0 opinion that clarifies the scope of environmental effects analysis under the National Environmental Policy Act (NEPA) and requires substantial judicial deference to federal agencies in NEPA cases. This decision has broad implications for public agencies and Tribal Nations involved in infrastructure and economic development projects, natural resources management, water supply project operations and other matters where there is a federal nexus. … For local communities, water agencies, and Tribal Nations with projects that depend on the NEPA process, this ruling offers a couple of key takeaways. The first is straightforward. The scope of environmental effects analyzed in an EIS will continue to be limited by the authority of the federal agency. … A more complex implication relates to judicial deference—particularly deference to a federal agency’s choice of alternatives and its feasibility analysis.