Gage v. Pumpelly & Others was a United States Supreme Court case that addressed the issue of whether a state court had the authority to issue an injunction against a federal court. The case arose when the plaintiff, Gage, sought an injunction from the state court of California against the defendants, Pumpelly and others, who were involved in a case before the federal court. The state court granted the injunction, and the defendants appealed to the Supreme Court. The Supreme Court held that the state court did not have the authority to issue an injunction against a federal court. The Court reasoned that the state court was not a court of competent jurisdiction to issue such an injunction, and that the federal court had exclusive jurisdiction over the case. The Court further held that the state court's action was an interference with the federal court's jurisdiction, and thus was unconstitutional. The Court's decision in Gage v. Pumpelly & Others established that state courts do not have the authority to issue injunctions against federal courts. This decision has been cited in numerous subsequent cases, and has been used to support the principle that federal courts have exclusive jurisdiction over cases involving federal law.

Justice Field delivered the dissenting opinion in Gage v. Pumpelly & Others, arguing that the majority's decision was contrary to established law and precedent. He argued that under existing laws of California, a mining claim could not be forfeited for non-payment of taxes unless it had been assessed as real estate or personal property; since this particular claim had only been assessed as a mine, it should not have been subject to forfeiture due to unpaid taxes. Furthermore, he noted that even if such claims were subject to taxation by virtue of their being located on public lands owned by the United States government, they would still need to be taxed according to state law rather than federal statutes. Finally, Justice Field pointed out that Congress had never passed any legislation specifically authorizing states like California from taxing mines located on public land within its borders; thus there was no legal basis for doing so in this case either.