White v. Greenhow, Treasurer was a United States Supreme Court case that dealt with the issue of whether a state could tax the income of a federal employee. The case was brought by William White, a federal employee, who argued that the state of Virginia had no right to tax his income. The state of Virginia argued that it had the right to tax the income of federal employees, as it was a state tax and not a federal tax. The Supreme Court ultimately sided with White, ruling that the state of Virginia did not have the right to tax the income of federal employees. The Court reasoned that the federal government had exclusive authority over the taxation of federal employees, and that the state of Virginia could not interfere with this authority. The Court also noted that the state of Virginia had not provided any evidence that the tax was necessary to support the state government. The decision in White v. Greenhow, Treasurer was an important one, as it established that the federal government had exclusive authority over the taxation of federal employees. This decision has been cited in numerous cases since, and has been used to support the idea that the federal government has exclusive authority over the taxation of federal employees.

Justice Field delivered the dissenting opinion in White v. Greenhow, Treasurer. He argued that the Court should not have granted a writ of mandamus to compel payment from the state treasurer as it was an act of political discretion and therefore beyond judicial review. The plaintiff had sought compensation for services rendered to Virginia during its secession from the Union prior to being readmitted into it after Reconstruction, but Justice Field maintained that such claims were matters of policy which could only be decided by Congress or other legislative bodies rather than courts. Furthermore, he noted that even if there had been a contract between Virginia and White at one point in time, any obligation arising out of this agreement would have been extinguished when Virginia seceded from the Union since contracts with states are considered void under federal law once they leave the United States. As such, Justice Field concluded that granting relief on behalf of White would amount to an unconstitutional interference with state sovereignty and thus must be denied by this Court.