Newhall v. Sanger was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of mandamus to a federal court. The case arose when the plaintiff, Newhall, sought to have the defendant, Sanger, removed from his position as a federal court judge. Newhall argued that Sanger had been appointed to the position without the proper qualifications and that he had acted in a manner that was prejudicial to the interests of the plaintiff. The Supreme Court held that the state court did not have the authority to issue a writ of mandamus to a federal court. The Court reasoned that the writ of mandamus was a remedy that was available only to the federal courts and that the state court did not have the power to interfere with the federal court's decision. The Court also held that the plaintiff had failed to show that Sanger had acted in a manner that was prejudicial to the plaintiff's interests. As a result, the Court dismissed the plaintiff's case.

In Newhall v. Sanger, the Supreme Court was asked to decide whether a contract between two parties could be enforced despite one of them having died before it had been fully executed. The majority opinion held that the contract was not enforceable since it had not been completed prior to the death of one party and thus could not be binding on their estate or heirs. However, in dissent Justice Miller argued that contracts should generally be upheld if they are otherwise valid and have been partially performed by both parties prior to any intervening event such as death or bankruptcy which would prevent full execution of the agreement. He noted that this rule is necessary for fairness in order for people who enter into agreements with good faith intentions to receive some benefit from their efforts even when circumstances beyond their control prevent completion of all contractual obligations.