Congress authorized States to require interstate motor carriers operating within their borders to register with the State proof of their Interstate Commerce Commission (ICC) interstate operating permits. Prior to 1994, the ICC allowed States to charge interstate motor carriers annual registration fees of up to $10 per vehicle. The Participating States would issue a stamp for each of the carrier's vehicles. This system came to be known as the 'bingo card' system. Congress directed the ICC to implement a new system to replace the 'bingo card' regime. Under the Single State Registration System, 'a motor carrier would be required to register annually with only one State,' and 'such single State registration would be deemed to satisfy the registration requirements of all other States. One State would -- on behalf of all other participating States -- register a carrier's vehicles, file and maintain paperwork, and collect and distribute registration fees. Participation was limited to those States that had elected to participate in the 'bingo card' system. The fees charged were not to be more than $10 per vehicle per state. Left open by the regulations was whether, under the Single State Registration System, States were free to terminate 'reciprocity agreements' that were in place under the 'bingo card' regime. Eventually after notice and comment the ICC concluded that its preliminary view on reciprocity agreements was inconsistent with ISTEA's fee-cap provision and with 'the intent of the law that the flow of revenue for the States be maintained while the burden of the registration system for carriers be reduced.' The United States Court of Appeals for the District of Columbia concluded that the plain language of the statute supported the ICC's determination that States participating in the new system must consider reciprocity agreements. Michigan had participated in the 'bingo card' system. Michigan also participated in reciprocity agreements. P is headquartered in Kansas. P's trucks that were licensed in Illinois. Michigan had a reciprocity agreement with Illinois. Michigan changed its reciprocity policy to the State in which a carrier maintained its principal place of business rather than the State in which individual vehicles were licensed. P got the bill in the mail. P paid and sued for a refund. P alleged that, because Michigan had not 'collected or charged' a fee for the 1991 registration year for trucks licensed in Illinois, ISTEA's fee-cap provision prohibits Michigan from levying a fee on Illinois-licensed trucks. P prevailed in court and on appeal. The Michigan Supreme Court reversed; reciprocity agreements are not relevant in determining what fee a State charged or collected as of November 15, 1991. The Court applied Chevron but determined that the statute unambiguously forbids the ICC's interpretation. The Supreme Court granted certiorari.