The Montana Supreme Court ruled on October 13, 2026, that Yellowstone County must comply with state stormwater management regulations. This decision affects the County's ability to manage stormwater discharges, which are crucial for protecting water quality. The ruling clarifies the authority of local governments in relation to environmental regulations.
In this case, Yellowstone County appealed a decision from the Thirteenth Judicial District Court. The County sought a declaration that it lacked the authority to comply with certain requirements set by the Montana Department of Environmental Quality (DEQ) under Admin. R. M. 17.30.1111(6) (2022). The County argued that these requirements constituted an unfunded mandate, meaning they imposed obligations without providing necessary funding.
The parties involved in this case are Yellowstone County, represented by Deputy Yellowstone County Attorney Steve Williams, and the Montana Department of Environmental Quality, represented by Staff Attorney Kurt R. Moser. The dispute arose after the County was required to apply for a permit to discharge stormwater as part of the federal Clean Water Act (CWA) regulations, which the state of Montana administers.
Yellowstone County, which includes areas outside the City of Billings, initially declined to apply for the necessary permit due to concerns about its authority and funding. The Environmental Protection Agency (EPA) ordered the County to either cease stormwater discharges or apply for the permit. In response, the County filed a declaratory-judgment action in January 2024 while simultaneously applying for permit coverage.
On May 12, 2025, the District Court granted summary judgment to DEQ and denied Yellowstone County's motion. The court concluded that the County had the authority to implement the required stormwater management measures and that the requirements did not constitute an unfunded mandate. The County then appealed this ruling to the Montana Supreme Court.
The Montana Supreme Court, led by Justice Katherine M. Bidegaray, affirmed the District Court's decision. The court ruled that Yellowstone County must obtain coverage under the Montana Pollutant Discharge Elimination System (MPDES) permit and implement the stormwater management measures as required. Justice Bidegaray stated, "Yellowstone County must obtain MPDES permit coverage and must satisfy the storm water requirements for which its permit makes it responsible through one or more lawful means."
The court clarified that while Yellowstone County has certain powers, it cannot claim a lack of authority to implement the required measures. The ruling emphasized that the County must use lawful means to comply with the permit requirements, which include six minimum control measures mandated by the EPA and adopted by Montana.
This ruling is significant as it reinforces the authority of state regulations in managing stormwater and protecting water quality. It also highlights the responsibilities of local governments under federal and state environmental laws. The decision may set a precedent for how counties in Montana and potentially other states handle similar environmental compliance issues.
The impact of this ruling extends beyond Yellowstone County. It serves as a reminder to local governments about their responsibilities in environmental management. The court's decision may influence how other counties approach stormwater management and compliance with environmental regulations, particularly in light of federal mandates.
Looking ahead, Yellowstone County has the option to appeal the ruling, but it remains to be seen if they will pursue further legal action. There are no related cases pending that could directly affect this ruling, but the implications of this decision may resonate in future environmental law cases across the state.