Harris v. McGovern 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 habeas corpus to a prisoner who was being held in a federal prison. The case arose when a prisoner, Harris, was held in a federal prison in the state of Pennsylvania. Harris sought a writ of habeas corpus from the state court, claiming that he was being held in violation of the Constitution. 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 power to interfere with the federal government's authority 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 person's detention, and not to challenge the conditions of the detention. The Court's decision in Harris v. McGovern established that state courts do not have the authority to issue writs of habeas corpus to prisoners held in federal prisons. This decision has been cited in numerous subsequent cases, and has been used to support the principle that state courts cannot interfere with the federal government's authority to imprison individuals.

Justice Field delivered the dissenting opinion in Harris v. McGovern, arguing that the majority's decision was contrary to established legal principles and would lead to an unjust result. He argued that a contract must be interpreted according to its plain language, which should not be altered by extrinsic evidence or judicial construction. In this case, he believed that the agreement between Harris and McGovern was clear: it provided for payment of $1 per acre for all land purchased from McGovern up until January 1st 1873; any purchases after this date were excluded from consideration under the terms of their agreement. The majority had instead chosen to interpret "January 1st" as meaning December 31st - a change which Justice Field found unacceptable since it contradicted both parties' intentions when they entered into their contract and violated basic rules of interpretation regarding contracts. Furthermore, Justice Field noted that if such changes could be made without consent then no one's contractual rights would ever truly be secure since courts could always find some way around them through creative interpretations or re-definitions of words used in agreements.