In POST v. SUPERVISORS, the United States Supreme Court was asked to decide whether a state statute that allowed for the taxation of certain property was constitutional. The statute in question allowed for the taxation of property owned by a corporation, but not of property owned by individuals. The plaintiff, POST, argued that the statute violated the Fourteenth Amendment of the United States Constitution, which states that no state shall "deny to any person within its jurisdiction the equal protection of the laws." The Supreme Court agreed with POST, ruling that the statute was unconstitutional. The Court held that the statute violated the Equal Protection Clause because it treated corporations differently than individuals, without any rational basis for doing so. The Court also held that the statute was not a valid exercise of the state's power to tax, as it was not based on any reasonable classification. The Court concluded that the statute was an arbitrary and unreasonable discrimination against corporations, and thus violated the Equal Protection Clause.

Justice Field delivered the dissenting opinion in Post v. Supervisors, arguing that the majority's decision was incorrect and should be reversed. He argued that Congress had not intended to grant a right of appeal from decisions made by county supervisors when it passed the act in question, which only provided for appeals from decisions of district courts or other tribunals established under federal law. Furthermore, he noted that if such an appeal were allowed then any party aggrieved by a decision of local officials could bring their case before a federal court without having first exhausted all available remedies at state level as required by law. In conclusion, Justice Field maintained that allowing this type of appeal would lead to unnecessary interference with state laws and proceedings and thus should not be permitted under existing legislation.