In the 1899 case of Plummer v. Coler, the U.S. Supreme Court ruled on a dispute involving taxation and interstate commerce. The plaintiff, Plummer, was a New York resident who owned stock in several corporations that did business but were not incorporated in New York State. The defendant, Coler (the tax commissioner), assessed taxes on these stocks under a state law taxing personal property at its location within the state regardless of where its owner lived. Plummer argued this violated his constitutional rights by impeding interstate commerce and depriving him of his property without due process. The court upheld the constitutionality of New York's tax law stating it didn't interfere with interstate commerce as it taxed only those shares belonging to residents which represented capital within its borders; thus no multiple states were involved for an issue with Commerce Clause to arise. Furthermore, they found no violation of due process because shareholders are considered owners of corporate property proportionate to their shareholding percentage; hence states can levy taxes accordingly.

In the dissenting opinion for Plummer v. Coler, Justice Harlan argued that the majority's decision to uphold a tax on commercial agents selling goods in New York manufactured outside of the state was unconstitutional. He contended that this ruling violated both the Commerce Clause and Equal Protection Clause of the Constitution. According to him, it interfered with interstate commerce by imposing an unjust burden on out-of-state manufacturers while favoring local ones, thus creating unfair competition. Furthermore, he believed it denied equal protection under law as it discriminated against non-residents conducting business within New York State boundaries. Therefore, Justice Harlan disagreed with his colleagues' interpretation of constitutional provisions and their application in this case.