The court of appeals affirmed a judgment of the district court. The court held that an air pollution control district’s rules requiring registration of and fees for diesel engines used in agricultural operations and setting emission standards for stationary diesel engines were not preempted by the federal Clean Air Act.
The Monterey Bay Unified Air Pollution Control District in 2007 adopted and began enforcing rules regulating diesel-powered engines. In particular, Rule 220 required owners or operators of diesel engines to register with the District any diesel engine of 50 brake horsepower or larger used in agricultural operations. Rule 310 imposed application fees and annual registration fees on the owners and operators of engines that were subject to Rule 220’s requirements.
