Poindexter 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 officer. The case was brought by William Poindexter, a federal officer, who was being taxed by the state of Virginia on his income. Poindexter argued that the state of Virginia had no right to tax his income because he was a federal officer and the state was infringing on the federal government's power. The Supreme Court ruled in favor of Poindexter, holding that the state of Virginia had no right to tax the income of a federal officer. The Court reasoned that the federal government had exclusive power over the salaries of its officers and that the state of Virginia was infringing on that power by attempting to tax Poindexter's income. The Court also held that the state of Virginia was violating the Supremacy Clause of the Constitution, which states that federal law is supreme over state law. The Court's decision in Poindexter v. Greenhow, Treasurer was an important one in terms of federalism and the power of the federal government. It established that the federal government has exclusive power over the salaries of its officers and that states cannot interfere with that power by attempting to tax the income of federal officers.

In Poindexter v. Greenhow, Treasurer, the Supreme Court was asked to decide whether a Virginia statute that allowed for the sale of property owned by debtors who had failed to pay their taxes violated the Fourteenth Amendment's Due Process Clause. The majority opinion held that it did not violate due process because there were sufficient safeguards in place to protect taxpayers from arbitrary action and ensure they received fair notice of any proceedings against them. Justice Field dissented on this point, arguing that while some procedural protections existed under state law, they were inadequate when compared with those provided by federal statutes governing similar matters. He argued further that even if these procedures were adequate at face value, they could still be abused or manipulated in such a way as to deprive citizens of their constitutional rights without proper judicial review or oversight. As such he concluded that the Virginia statute was unconstitutional and should be struck down as violative of due process guarantees afforded by both state and federal laws.