In the case of Michael Fitzgerald, Treasurer of Iowa v. Racing Association of Central Iowa et al., 2002, the U.S. Supreme Court ruled on a dispute over tax rates for different types of gambling in Iowa. The state had imposed a significantly higher tax rate on revenues from slot machines at racetracks compared to those aboard riverboats. The Racing Association argued that this was discriminatory and violated their equal protection rights under the Fourteenth Amendment. The Supreme Court disagreed with this argument, ruling in favor of Fitzgerald by a vote of 6-3. They found that there was no violation because both forms were not similarly situated entities due to differences in regulation and history between riverboat gambling and racetrack gambling; therefore they could be taxed differently without violating equal protection laws. Justice Stephen Breyer wrote for the majority stating that "the dissimilar treatment is directly related to achieving an important governmental objective." This decision upheld states' rights to regulate industries within their borders as long as it does not violate constitutional protections.

In the dissenting opinion for the case between Michael Fitzgerald, Treasurer of Iowa and Racing Association of Central Iowa et al., Justice Thomas argued that differential tax rates on different forms of gambling did not violate equal protection under the Fourteenth Amendment. He stated that it was within a state's rights to implement such taxes as they saw fit, provided there was some rational basis for doing so. In this case, he believed there was - slot machines at racetracks had been taxed more heavily than those on riverboats because they were seen as more harmful due to their greater accessibility. Furthermore, he pointed out that previous cases have upheld similar distinctions in taxation based on differences in business structure or location. Therefore, according to Justice Thomas' dissenting view, the majority decision incorrectly expanded equal protection doctrine by striking down a legitimate exercise of state power.