Denver v. Roane 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 City of Denver and the estate of a deceased non-resident, William Roane. Roane had died in 1876, leaving an estate of $50,000 in the City of Denver. The City of Denver sought to tax the estate, claiming that it had the right to do so under the Colorado Constitution. The Supreme Court held that the City of Denver did not have the right to tax the estate of a non-resident. The Court reasoned that the Colorado Constitution did not grant the City of Denver the power to tax the estate of a non-resident. Furthermore, the Court held that the power to tax the estate of a non-resident was a power reserved to the state, and not to the City of Denver. The Court's decision in Denver v. Roane established that a state cannot tax the income of a non-resident. This decision has been cited in numerous subsequent cases, and has been used to support the principle that a state cannot tax the income of a non-resident.

In Denver v. Roane, the Supreme Court was tasked with deciding whether a city ordinance that prohibited the sale of intoxicating liquors within four miles of an Indian reservation was constitutional. The majority opinion held that it was not, as Congress had exclusive authority to regulate commerce on Indian reservations and thus preempted any state or local laws from doing so. Justice Field dissented from this decision, arguing that while Congress did have exclusive power over matters concerning Indians and their lands, they could not interfere with a state's police powers in order to protect its citizens' health and welfare. He argued further that since this case involved only liquor sales outside of the reservation itself - which were subject to regulation by both federal law and local ordinances - there should be no conflict between them. Therefore he concluded that the ordinance in question should be upheld as valid under both federal law and Colorado's police powers.