Respondent's (R) argued that they should not be required to pay reparations on rates that they charged that were approved by the ICC based on a court finding that those rates were unreasonable. R was ordered to pay a reparation for the ICC rates that it charged various customers. R refused the order of the Commission and Arizona (P) sued in District Court and recovered judgment. Under the statute, transportation companies were required to file and publish tariffs. Any deviation from published rates was declared to be a criminal offense and a civil wrong giving rise to an action for damages from the injured shipper. Modifications to that basic policy were instituted in 1920 and granted the commission power to fix the maximum reasonable rate and the maximum and minimum limits within which a carrier's published rate must come. The Court of Appeals reversed. The Supreme Court granted certiorari.