States have the power to regulate intrastate commerce within their own state. They have very limited power with regard to interstate commerce (limited, very roughly, to nondiscriminatory regulation of transactions within the state which impact interstate commerce and where such regulation also is not in conflict with federal regulation of interstate commerce), because interstate commerce is expressly Constitutionally a federal function, and state action in that domain otherwise interferes with that federal function. A more expansive view of the federal power here narrows, rather than expands, the state power.