Marsh v. Nichols was a United States Supreme Court case that addressed the issue of whether a state could require a non-resident to pay a tax on the income they earned in the state. The case was brought by a resident of New York, who had earned income in the state of Connecticut. The state of Connecticut had imposed a tax on the income earned by non-residents, and the plaintiff argued that this was a violation of the privileges and immunities clause of the United States Constitution. The Supreme Court held that the tax was constitutional, as it did not discriminate against non-residents. The Court reasoned that the tax was a legitimate exercise of the state's power to tax, and that it was not a violation of the privileges and immunities clause. The Court also noted that the tax was not excessive, and that it was not an undue burden on non-residents. In conclusion, the Supreme Court held that the state of Connecticut was within its rights to impose a tax on the income earned by non-residents. The Court found that the tax was not a violation of the privileges and immunities clause, and that it was not an undue burden on non-residents.

In Marsh v. Nichols, the Supreme Court was asked to decide whether a state law that allowed for the sale of public lands at auction violated the Fourteenth Amendment's Equal Protection Clause. The majority opinion held that it did not violate this clause because there were no discriminatory classifications in place and thus no unequal treatment of individuals or groups. However, Justice Field dissented from this decision on two grounds: first, he argued that any classification based solely on race is inherently unconstitutional; second, he contended that even if such a classification could be justified as necessary to achieve some legitimate governmental purpose (which he believed was not true in this case), it must still be shown to bear some reasonable relation to achieving said purpose. As such, Justice Field concluded that since there was no evidence presented showing how racial classifications would help further any legitimate governmental interest here, they should have been declared unconstitutional by the court.