In the case of Sanford v. Kepner in 1952, the United States Supreme Court addressed a dispute over whether federal courts had jurisdiction to hear cases involving state tax laws. The plaintiff, Sanford, was an Arizona resident who sought to recover taxes paid under protest from the defendant, Kepner, who was a California official responsible for collecting inheritance taxes. The Ninth Circuit Court of Appeals ruled that it did not have jurisdiction because federal law prohibits lower federal courts from interfering with state taxation processes unless there is no plain and adequate remedy at law available in state court. The Supreme Court affirmed this decision on appeal by holding that since there were sufficient remedies available within California's legal system for challenging its tax laws (including refund suits), it would be inappropriate for a federal court to intervene. This ruling reinforced principles of comity between states and their respective sovereignty over internal matters such as taxation.

In the dissenting opinion for Sanford v. Kepner, Justice Frankfurter argued that the majority's decision was inconsistent with previous rulings and undermined principles of federalism. He contended that allowing a defendant to be tried twice for the same crime in both state and federal courts violated protections against double jeopardy enshrined in the Fifth Amendment. According to him, this ruling would lead to unnecessary retrials and could potentially result in conflicting verdicts from different jurisdictions on identical charges. Furthermore, he believed it disregarded states' rights by permitting federal courts to intervene unnecessarily in matters traditionally reserved for state jurisdiction under our system of dual sovereignty.