Tilghman v. Proctor was a United States Supreme Court case that addressed the issue of whether a state court could enjoin a federal court from hearing a case. The case involved a dispute between two parties over a contract for the sale of a steamboat. The plaintiff, Tilghman, had filed a suit in the federal court to recover damages for the breach of the contract. The defendant, Proctor, then filed a suit in the state court to enjoin the federal court from hearing the case. The Supreme Court held that the state court did not have the power to enjoin the federal court from hearing the case. The Court reasoned that the state court was not authorized to interfere with the proceedings of the federal court, as the federal court had exclusive jurisdiction over the case. The Court further noted that the state court could not interfere with the proceedings of the federal court, as this would be a violation of the Supremacy Clause of the United States Constitution. The Court's decision in Tilghman v. Proctor established the principle that state courts cannot interfere with the proceedings of federal courts. This principle has been applied in numerous cases since then, and it remains an important part of the American legal system today.

In Tilghman v. Proctor, the Supreme Court was asked to decide whether a contract between two parties that had been partially performed could be enforced by one of the parties against the other. The majority opinion held that it could not, as there was no consideration for any part of the agreement which had yet to be fulfilled. However, in dissent Justice Field argued that when an agreement is made and some performance has already taken place on both sides then this should constitute sufficient consideration for enforcing all parts of the contract regardless if they have yet to be completed or not. He further stated that such contracts are binding upon both parties and can only be avoided through mutual consent or legal excuse such as fraud or mistake.