Supervisors v. Galbraith was a United States Supreme Court case that addressed the issue of whether a state could tax the income of a non-resident. The case involved a dispute between the Supervisors of the County of San Francisco and the defendant, John Galbraith. Galbraith was a resident of the state of Nevada, but he owned property in San Francisco and received income from it. The Supervisors argued that they had the right to tax Galbraith's income, while Galbraith argued that the state of Nevada had exclusive jurisdiction over his income. The Supreme Court ultimately sided with Galbraith, ruling that the state of Nevada had exclusive jurisdiction over his income. The Court reasoned that the Constitution of the United States did not grant the states the power to tax the income of non-residents, and that the power to tax was reserved to the states in which the income was earned. The Court also noted that the power to tax was an important part of the sovereignty of the states, and that it should not be interfered with by other states. The decision in Supervisors v. Galbraith established the principle that states cannot tax the income of non-residents. This principle has been applied in numerous cases since then, and it remains an important part of the law today.

Justice Field delivered the dissenting opinion in Supervisors v. Galbraith, arguing that the majority's decision was contrary to both law and justice. He argued that a tax imposed on property owners for improvements made by them should be considered an assessment of benefits rather than a general tax, as it is not based on any fixed rule or standard but instead depends upon the value of each individual's property before and after improvement. Furthermore, he noted that such taxes are often used to finance public works projects which benefit all citizens equally regardless of their wealth or social status; thus they do not constitute an unconstitutional taking from individuals without due process of law. Finally, Justice Field concluded his dissent by noting that while there may be some instances where taxation could become oppressive if applied indiscriminately across all classes of people, this case did not present one such instance since only those who benefited from improvements were taxed accordingly.