Mills v. Scott was a United States Supreme Court case that dealt with the issue of whether a state could constitutionally impose a tax on the income of a non-resident. The case was brought by a resident of the state of Virginia, who argued that the state's income tax was unconstitutional because it discriminated against non-residents. The Supreme Court held that the tax was constitutional, as it did not violate the Equal Protection Clause of the Fourteenth Amendment. The Court reasoned that the tax was not discriminatory because it applied equally to all non-residents, regardless of their state of residence. Furthermore, the Court held that the tax was not an undue burden on interstate commerce, as it did not interfere with the free flow of goods and services between states. The Court also noted that the tax was not an unreasonable burden on non-residents, as it was based on the same principles as taxes imposed on residents. Ultimately, the Court held that the tax was constitutional, as it did not violate the Equal Protection Clause of the Fourteenth Amendment. The Court's decision in Mills v. Scott established that states could constitutionally impose taxes on the income of non-residents, provided that the tax was applied equally to all non-residents and did not interfere with interstate commerce.

In Mills v. Scott, the United States Supreme Court was asked to decide whether a state law that prohibited African Americans from voting in elections violated the Fifteenth Amendment of the U.S. Constitution which prohibits states from denying citizens their right to vote based on race or color. The majority opinion held that it did not violate this amendment because it applied equally to all races and therefore did not discriminate against any particular group of people. Justice Field dissented, arguing that while the law may have been facially neutral, its purpose was clearly discriminatory as evidenced by its history and context - namely, Mississippi's long history of racial discrimination in voting rights laws prior to passage of this statute. He argued further that even if there were no explicit intent behind this statute, its effect would be discriminatory since African Americans would be disproportionately affected by such a restriction on their ability to exercise their constitutional right to vote due solely to their race or color