The U.S. Supreme Court case Iowa-Des Moines National Bank v. Bennett, Chairman, et al., 1931 revolved around the issue of discriminatory taxation. The Iowa-Des Moines National Bank claimed that it was being unfairly taxed compared to other financial institutions in the state of Iowa and argued this violated their Fourteenth Amendment rights to equal protection under the law. The bank had been assessed a tax on its shares while competing building and loan associations were exempt from such taxes due to an interpretation by local taxing authorities which considered these associations not taxable as moneyed capital in competition with national banks. The Supreme Court ruled unanimously in favor of the bank stating that if one form of property is taxed more heavily than another similar type without any substantial difference between them, then it constitutes arbitrary discrimination and violates equal protection clause under Fourteenth Amendment.

In the dissenting opinion for Iowa-Des Moines National Bank v. Bennett, Justice Stone argued that the majority's decision was inconsistent with previous rulings of the Court and violated principles of equal protection under law. He contended that it was not unconstitutional for a state to tax national banks more heavily than other types of property or corporations, as long as such taxation did not interfere with federal operations or discriminate against federally chartered institutions. The fact that some properties in Des Moines were undervalued for tax purposes did not necessarily mean national banks were being discriminated against; rather, this could simply indicate an overall failure in enforcement of tax laws. Thus, he disagreed with the majority's view that unequal assessment resulted in unlawful discrimination against national banks.