Robbins v. Shelby County Taxing District was a United States Supreme Court case that addressed the issue of taxation of railroad property. The case was brought by the plaintiff, Robbins, who was the owner of a railroad in Shelby County, Tennessee. Robbins argued that the county had imposed an unconstitutional tax on his railroad property. The county argued that the tax was valid because it was imposed in accordance with the state's taxing laws. The Supreme Court held that the tax was unconstitutional because it violated the Due Process Clause of the Fourteenth Amendment. The Court reasoned that the tax was not based on any rational basis and was therefore arbitrary and unreasonable. The Court also held that the tax was not a valid exercise of the state's taxing power because it was not based on any reasonable relationship between the amount of the tax and the value of the property. The Court's decision in Robbins v. Shelby County Taxing District established that taxes must be based on a rational basis and must be related to the value of the property in order to be valid. This decision has been cited in numerous subsequent cases involving taxation of property.

Justice Harlan delivered the dissenting opinion in Robbins v. Shelby County Taxing District, arguing that the majority's decision was contrary to precedent and established principles of taxation law. He argued that a state cannot impose taxes on property owned by citizens of another state without violating the privileges and immunities clause of Article IV, Section 2 of the Constitution. The Court had previously held in Ward v. Maryland (1880) that such an act would be unconstitutional because it discriminates against non-residents who are not subject to similar taxation within their own states. Justice Harlan further noted that this case involved a tax imposed upon personal property located outside Tennessee, which is even more objectionable than taxing real estate situated outside its borders as it does not benefit from any services provided by Tennessee or its municipalities for which they might reasonably expect compensation through taxation. In conclusion, he asserted that if allowed to stand, this ruling could lead to other states imposing discriminatory taxes on out-of-state residents with impunity and thus violate one of our most fundamental constitutional rights - equal protection under the law regardless of residency status or origin