In 1983 petitioners brought suit in an Arkansas Chancery Court, alleging that the flat tax portion of that States Highway Use Equalization (HUE) tax discriminated against interstate commerce in violation of the Commerce Clause by imposing on out-of-state truckers greater per-mile costs than those imposed on in-state truckers, who are likely to drive many more miles on the States highways. Petitioners sought a refund of all HUE taxes paid. In affirming the Chancery Courts ruling that the tax was constitutional, the State Supreme Court relied on this Courts decisions upholding flat taxes in Capitol Greyhound Lines v. Brice, 339 U.S. 542, Aero Mayflower Transit Co. v. Board of Railroad Commrs of Mont. 332 U.S. 495, and Aero Mayflower Transit Co. v. Georgia Public Service Commn, 295 U.S. 285, and explicitly rejected petitioners argument that Complete Auto Transit, Inc. v. Brady, 430 U.S. 274, overruled the Aero Mayflower line of cases. On June 23, 1987, this Court ruled, in American Trucking Assns., Inc. v. Scheiner, 483 U.S. 266, that un