This case requires us to decide whether a special tax imposed by the state of Missouri on rentals derived from the leasing of railroad cars violates federal law prohibiting state taxes that discriminate against *1302railroads. The plaintiff freight-line companies filed their complaint in the District Court1 against the State Tax Commission of Missouri and the Director of the Department of Revenue of the State of Missouri,2 alleging that Missouri’s Private Car Tax, Mo.Rev.Stat. Ch. 152 (1986), violates Section 306(l)(d) of the Railroad Revitalization and Regulatory Reform Act of 1976, Pub.L. No. 94-210, 90 Stat. 31, codified at 49 U.S.C. § 11503 (1988) (“the 4-R Act”). The District Court granted the plaintiffs’ motion for summary judgment and permanently enjoined the state from assessing, levying, or collecting any taxes pursuant to the Private Car Tax. The state appeals. We affirm.
Section 306 of the 4-R Act states in relevant part that “[i]t is unlawful for a State ... to commit any of the following prohibited acts ... (d) The imposition of any other tax which results in discriminatory treatment of a common carrier by railroad subject to this part.”3 90 Stat. at 54. Section 306 thus forbids all taxes that discriminate against railroads (not just discriminatory property'taxes) and covers the plaintiffs in this case, who are engaged in the business of leasing railroad cars to railroads that use the leased cars in their interstate operations. See Trailer Train v. Bair, 765 F.2d 744, 745 (8th Cir.), cert, denied, 47.4 U.S. 1021, 106 S.Ct. 572, 88 L.Ed.2d 556 (1985).4 The issue before us is whether the Private Car Tax, which applies only to freight line companies such as the plaintiffs, Mo.Rev.Stat. §§ 152.010-152.030, violates the 4-R Act’s prohibition against “any other tax which results in discriminatory treatment.” 5
The state argues that Section 306 requires a finding of actual discriminatory effect, because only those taxes that “result” in discriminatory treatment are prohibited. To determine whether the Private Car Tax brings about such a result, the state contends, the District Court should have conducted an in-depth examination of Missouri’s complete tax structure as it applies to the plaintiffs and to other businesses; if the Private Car Tax is in essence an equivalent (or, as detailed analysis might reveal, an even less burdensome) substitute for another tax of general applicability, then it does not violate Section 306.
This argument, however, runs contrary to both Supreme Court and Eighth Circuit precedent. In Arizona Pub. Serv. Co. v. Snead, 441 U.S. 141, 99 S.Ct. 1629, 60 L.Ed.2d 106 (1979), the Supreme Court dealt with the issue of whether a New Mexico state tax on electricity, which in effect applied only to electricity generated in New Mexico and sold out of state, violated a federal statute prohibiting taxes on electricity that were discriminatory against out-of-state consumers. Snead, 441 U.S. at 143-47, 99 S.Ct. at 1631-33. The federal statute defined a discriminatory tax as one that “results, either directly or indirectly, in a greater tax burden on electricity which is generated and transmitted in interstate commerce than on electricity which is generated and transmitted in intrastate commerce.” Id. at 146, 99 S.Ct. at 1632 (citation omitted). The state argued that an examination of New Mexico’s entire tax structure was required to determine whether or not the electricity tax violated the federal statute. Id. at 149, 99 S.Ct. at *13031633. The Supreme Court rejected this argument, saying
the federal statutory provision is directed specifically at a state tax “on or with respect to the generation or transmission of electricity,” not to the entire tax structure of the State. The tax imposed by New Mexico[ ] ... is concededly a tax on the generation of electricity.... To look narrowly to the type of tax the federal statute names, rather than to consider the entire tax structure of the State, is to be faithful not only to the language of that statute but also to the expressed intent of Congress in enacting it. Because the ... tax itself indirectly but necessarily discriminates against electricity sold outside New Mexico, it violates that federal statute.
Id. at 149-50, 99 S.Ct. at 1634 (emphasis in original).
In Ogilvie v. State Bd. of Equalization, 657 F.2d 204 (8th Cir.), cert. denied, 454 U.S. 1086, 102 S.Ct. 644, 70 L.Ed.2d 621 (1981), the state of North Dakota argued that its tax system was equitable and not violative of Section 306 because the higher property tax imposed upon railroads was offset by a business privilege tax that other businesses were required to pay and railroads were not. Ogilvie, 657 F.2d at 207-10. We first quoted with approval the conclusion of the district court that “ ‘[t]he most obvious form of tax discrimination is to impose a tax on a class of rail transportation property that is not imposed on other nonrailroad property of the same class.’ ” Id. at 210. The Court then went on to state that “North Dakota's rationalization that they have an equitable tax system because of a business privilege tax is nothing more than an attempt to resurrect ... an exemption from § 306 for states with a ‘reasonable classification of property.’ Congress did not accept the proposal and this court will not accept it.” Id.
We are bound by the reasoning of Snead and Ogilvie. The Private Car Tax is imposed solely on freight line companies, who are among the intended beneficiaries of the protection granted by the 4-R Act. Although Section 306 prohibits only taxes that “result” in discriminatory treatment, a tax that applies only to one class of businesses necessarily discriminates against that class; under the 4-R Act it is not within our discretion to analyze the disputed tax in the context of Missouri’s overall tax structure. Snead, 441 U.S. at 150, 99 S.Ct. at 1634, Ogilvie, 657 F.2d at 210. “The 4-R Act ... is a prophylactic rule to prevent tax discrimination. It forbids some fair arrangements because the actual fairness of those arrangements is too difficult and expensive to evaluate.” Kansas City Southern By. v. McNamara, 817 F.2d 368, 375 (5th Cir.1987). “[T]he categorical language of the 4-R Act demands bright-line rules for simple judicial administration.” Id. at 378.6
The state challenges the holding of the District Court on two additional grounds. First, it argues that because some of the proceeds of the Private Car Tax are used to benefit railroads, the tax is not violative of the 4-R Act. This argument is without merit, as the use of the proceeds of a tax has no bearing on the question of whether the tax is discriminatory. Second, the state challenges the holding of the District Court on the grounds of comity. This issue is raised for the first time on appeal. We therefore decline to consider it. See Kelley v. Crunk, 713 F.2d 426, 427 (8th Cir.1983).7
We conclude that the District Court correctly held that Missouri’s Private Car Tax violates Section 306 of the 4-R Act and we *1304affirm its order permanently enjoining the state from assessing, levying, or collecting any taxes pursuant to the Private Car Tax.
. The Honorable Scott O. Wright, United States District Judge for the Western District of Missouri.
. In this opinion we refer to the defendants collectively as "the state."
. We use the language of Section 306, even though its codified version at 49 U.S.C. § 11503 is different. See Trailer Train Co. v. Leuenber-ger, 885 F.2d 415, 416 n. 2 (8th Cir.1988), cert, denied, 490 U.S. 1066, 109 S.Ct. 2065, 104 L.Ed.2d 630 (1989); Ogilvie v. State Bd. of Equalization, 657 F.2d 204, 206 n. 1 (8th Cir.), cert, denied, 454 U.S. 1086, 102 S.Ct. 644, 70 L.Ed.2d 621 (1981). For a more complete discussion of Section 306 and its legislative history, see Ogilvie, 657 F.2d at 206-08.
. The state does not contest the proposition that the plaintiffs, as lessors of railroad cars, are protected by the 4-R Act.
. The Private Car Tax requires freight line companies to pay a tax "equal to three percent of the total amount received for [railroad] car rentals by the freight line companies.” Mo.Rev.Stat. § 152.030.
. "It may be that in an appropriate case we would allow the state to save a facially discriminatory tax by showing that it is necessary to 'compensate' for some state or local tax ... that for some reason cannot be levied against the railroads." Kansas City Southern, 817 F.2d at 376 (emphasis in original). The state does not allege, however, that the Private Car Tax is a substitute for a generally applicable tax that is impossible to levy against lessors of railroad cars.
. In any event, this argument is foreclosed by our holding in Burlington Northern R.R. v. James, 911 F.2d 1297, 1300 (8th Cir.1990) ("The common law principle of federal deference to state tax schemes ... has no place in a § 306 analysis.”).