Wilmot v. Mudge 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, Wilmot, was held in a federal prison in Massachusetts. Wilmot 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 power, 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 fundamental right, and that the state court should not be allowed to interfere with the federal government's power to protect this right. In conclusion, 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 power, 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 fundamental right, and that the state court should not be allowed to interfere with the federal government's power to protect this right.

In Wilmot v. Mudge, the United States Supreme Court was tasked with deciding whether a state court had jurisdiction to hear a case involving federal law. The majority opinion held that the state court did not have jurisdiction and dismissed the case. Justice Field dissented from this decision, arguing that it would be unjust for parties who were unable to bring their claims in any other forum to be denied access to justice simply because of an issue of federal law being involved. He argued that if Congress had intended for such cases not to be heard by state courts then they should have explicitly stated so in legislation or regulations rather than leaving it up to judicial interpretation as was done here. Furthermore, he noted that there were many instances where both federal and state laws applied simultaneously and thus allowing these types of cases into state courts could help ensure uniformity between them when interpreting similar issues under different legal systems. Ultimately, Justice Field concluded his dissent by stating that denying access to justice based on jurisdictional grounds alone is contrary both "to sound public policy" and "the spirit of our institutions".