Dillon v. Barnard et al. was a United States Supreme Court case that addressed the issue of whether a state could impose a tax on the income of a non-resident. The case was brought by the plaintiff, John F. Dillon, who was a non-resident of the state of Iowa. He argued that the state's tax on his income was unconstitutional because it violated the Due Process Clause of the Fourteenth Amendment. The Supreme Court held that the state of Iowa had the right to impose a tax on the income of a non-resident. The Court reasoned that the Due Process Clause did not prohibit a state from taxing the income of a non-resident, as long as the tax was applied in a reasonable manner. The Court also noted that the tax was not discriminatory, as it applied equally to all non-residents. In conclusion, the Supreme Court held that the state of Iowa had the right to impose a tax on the income of a non-resident, as long as the tax was applied in a reasonable manner. The Court also noted that the tax was not discriminatory, as it applied equally to all non-residents. This decision established the principle that states have the right to tax the income of non-residents, as long as the tax is applied in a reasonable manner.

Justice Field delivered the dissenting opinion in Dillon v. Barnard et al., arguing that the majority's decision was contrary to established precedent and would lead to a great deal of confusion for future courts. He argued that, under prior decisions, it had been held that when an individual has acquired title by prescription or otherwise, he is entitled to all the rights which are incident thereto; including those arising from his possession of such property. The majority opinion stated that this rule did not apply if there were any intervening rights between him and his predecessor in title; however Justice Field disagreed with this interpretation as it contradicted previous rulings on similar matters. Furthermore, he noted how allowing such an exception could create uncertainty regarding who holds what rights over certain properties since one party may have obtained their right through prescription while another may have obtained theirs through some other means. Ultimately, Justice Field concluded by stating that the Court should adhere to its earlier precedents instead of creating new exceptions which might cause more harm than good in terms of legal certainty and clarity going forward.