The Upper Missouri Waterkeeper, Flathead Lakers and the Confederated Salish and Kootenai Tribes filed a lawsuit in January 2026 challenging the Environmental Protection Agency's (EPA) approval of Montana's repeal of science-based, numeric water quality standards for nitrogen and phosphorus. The suit argues that replacing these standards with "vague, unenforceable" rules (via HB 664) violates the Clean Water Act (CWA) and threatens Montana's water quality, fisheries, and public health.