In the case of New York ex rel. Rogers v. Graves et al., 1936, the U.S Supreme Court ruled on a matter concerning income tax law and foreign diplomats' immunity from it. The plaintiff was an English diplomat who had been living in New York for several years and earning income from investments in American corporations. He argued that as a foreign diplomat, he should be exempted from paying taxes on this investment income under international law principles granting diplomatic agents immunity from certain local laws. The court disagreed with his argument, ruling that while diplomats are indeed immune to some extent under international law, this does not extend to all aspects of domestic legislation - particularly those which do not directly interfere with their diplomatic functions or infringe upon their personal inviolability or dignity. Therefore, the court held that taxing a foreign diplomat's investment income did not violate any principle of international law since such taxation did not impede him performing his official duties nor offend his personal dignity.

In the dissenting opinion for New York ex rel. Rogers v. Graves, Justice Cardozo disagreed with the majority's decision to uphold a tax on non-resident attorneys practicing in New York state courts. He argued that this ruling violated both the Privileges and Immunities Clause of Article IV and the Commerce Clause of the U.S Constitution by discriminating against out-of-state lawyers. According to Justice Cardozo, an attorney’s right to practice law is not merely a privilege granted by individual states but rather a fundamental right protected under federal law which should be free from discriminatory taxation based on residency status. Furthermore, he contended that such taxes could potentially hinder interstate commerce as they might discourage out-of-state attorneys from representing clients in New York courts due to increased costs.