Merrill v. Yeomans was a United States Supreme Court case that addressed the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner who was being held in a federal prison. The case arose when a prisoner, William Yeomans, was held in a federal prison in Utah. Yeomans sought a writ of habeas corpus from the state court in Utah, claiming that he was being held in violation of his constitutional rights. The state court granted the writ, and the federal government appealed the decision to the Supreme Court. The Supreme Court held that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. The Court reasoned that the writ of habeas corpus was a federal remedy, and that the state court did not have the authority to interfere with the federal government's power to imprison individuals. The Court also noted that the writ of habeas corpus was a remedy that could only be used to challenge the legality of a prisoner's detention, and not to challenge the conditions of the prisoner's confinement. The Court's decision in Merrill v. Yeomans established that state courts do not have the authority to issue writs of habeas corpus to prisoners held in federal prisons. The decision also clarified the scope of the writ of habeas corpus, and established that it could only be used to challenge the legality of a prisoner's detention, and not to challenge the conditions of the prisoner's confinement.

In the case of Merrill v. Yeomans, the Supreme Court was tasked with determining whether a contract between two parties that had been partially performed by one party could be enforced against them if they failed to fulfill their obligations under it. The majority opinion held that such contracts were enforceable and should not be voided simply because one party had already partially fulfilled its obligations. However, Justice Field dissented from this opinion, arguing that partial performance did not necessarily mean that an agreement was binding on both parties and therefore should not be enforced in court. He argued further that allowing such agreements to stand would lead to injustice as it would allow for unequal bargaining power between the two parties involved in a contract dispute and thus result in unfair outcomes for those who are less powerful or knowledgeable about legal matters than their counterparties.