Gould v. Day 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 held in a federal prison. The case arose when a prisoner, John Gould, was held in a federal prison in California. Gould sought a writ of habeas corpus from the California Supreme Court, claiming that he was being held in violation of the Constitution. The California Supreme Court granted the writ, and the United States Supreme Court was asked to decide whether the state court had the authority to do so. The Supreme Court held that the state court did not have the authority to issue the writ of habeas corpus. The Court reasoned that the writ of habeas corpus was a federal remedy, and that the state court did not have the power to issue such a writ. The Court further held that the writ of habeas corpus was a remedy that could only be granted by a federal court. The Court concluded that the state court had no authority to issue the writ of habeas corpus to a prisoner held in a federal prison.

Justice Field delivered the dissenting opinion in Gould v. Day, arguing that the majority's decision was contrary to both precedent and common sense. He argued that a contract between two parties should be enforced as written, regardless of whether it is beneficial or detrimental to either party. Furthermore, he noted that if one party were allowed to unilaterally modify an agreement without consulting with the other party first, then contracts would become meaningless documents since they could not be relied upon by either side for their enforcement. Finally, Justice Field stated that while courts may have equitable powers which allow them to adjust contracts when necessary due to unforeseen circumstances or inequitable terms imposed on one of the parties involved in a contract dispute; however this power should only be used sparingly and judiciously so as not undermine public confidence in contractual agreements generally.