The Board of County Commissioners of La Plata County (Board) (defendant) enacted county regulations that required operators of oil and gas facilities to obtain county approval before constructing or installing the facilities. Bowen/Edwards Associates, Inc. and other mineral-interest owners (plaintiffs) in La Plata County (county) brought suit against the Board, seeking a declaratory judgment that the county regulations were preempted by the Colorado Oil and Gas Conservation Act (Act). The Act authorized the Colorado Oil and Gas Conservation Commission (Commission) to issue regulations to protect the health and safety of the public against drilling and other mineral operations. The trial court dismissed the plaintiffs’ suit. The court of appeals held that the Board’s regulations were totally preempted by the Act. Specifically, the court of appeals found that the Act evinced a legislative intent to completely occupy the field of oil and gas regulation within the state. The Board appealed.