The U.S. Supreme Court case Choctaw, Oklahoma & Gulf Railroad Company et al. v. Mackey, as County Treasurer of Hughes County, Oklahoma et al., 1920 revolved around the taxation of railroad properties in the state of Oklahoma. The Choctaw, Oklahoma & Gulf Railroad Company and other railroads challenged their tax assessments by county officials for being excessive and discriminatory compared to other commercial properties within the counties they operated in. They argued that this violated their rights under both federal law and the Fourteenth Amendment's Equal Protection Clause which prohibits states from denying any person within its jurisdiction equal protection under its laws. However, upon review by the Supreme Court it was determined that there was no evidence presented to support these claims or show a clear violation of constitutional rights on part of county officials who assessed taxes based on fair cash value rather than favoring one class over another. Therefore, while acknowledging potential discrepancies between assessment methods used for different types of property (railroad vs non-railroad), without concrete proof demonstrating intentional discrimination or unjust treatment against railroads specifically - such allegations were dismissed.

In the dissenting opinion for the case of Choctaw, Oklahoma & Gulf Railroad Company et al. v. Mackey, as County Treasurer of Hughes County, Oklahoma et al., Justice Holmes disagreed with the majority's decision to invalidate a tax imposed by Hughes County on railroad companies operating within its jurisdiction. He argued that there was no constitutional basis for striking down such a tax and emphasized that it is not within the purview of courts to interfere in matters related to taxation unless they clearly violate constitutional provisions or principles. The justice further contended that states have broad powers in levying taxes and these should be respected unless they infringe upon federal authority or rights protected under the Constitution.