D assesses a fee upon, and only upon, vehicles that engage in intrastate commercial operations--that is, on trucks that undertake point-to-point hauls between Michigan cities. Ps engage in both interstate and intrastate hauling, and asked the Michigan courts to invalidate the provision. Ps explained to the courts that trucks that carry both interstate and intrastate loads engage in intrastate business less than trucks that confine their operations to the Great Lakes State. Thus, they reasoned, that because D's fee is flat, it discriminates against interstate carriers and imposes an unconstitutional burden upon interstate trade. The Michigan Court of Claims rejected Ps' claim. In part, it held that the fee does not implicate the Commerce Clause because it falls only on intrastate, not interstate, commerce. The Michigan Court of Appeals affirmed. It did not agree that the intrastate nature sheltered the fee from Commerce Clause scrutiny. It rejected the claim because the statute 'regulates evenhandedly,' and because the record lacked any 'evidence that any trucking firm's route choices [were] affected by the imposition of the fee.' The Michigan Supreme Court denied petitioners leave to appeal. The Supreme court granted certiorari.