Pugh v. United States was a Supreme Court case that addressed the issue of whether a federal court had the power to issue a writ of habeas corpus to a prisoner held in a state prison. The case arose when a prisoner, William Pugh, was held in a state prison in Virginia and sought a writ of habeas corpus from a federal court. The Supreme Court held that the federal court did not have the power to issue the writ, as the power to issue such writs was reserved to the states. The Court reasoned that the power to issue writs of habeas corpus was a part of the state's police power, and that the federal government had no authority to interfere with the state's exercise of that power. The Court also noted that the power to issue writs of habeas corpus was a part of the state's sovereignty, and that the federal government could not interfere with the state's exercise of that power. The Court concluded that the federal court did not have the power to issue the writ of habeas corpus to Pugh. As a result, Pugh was not released from prison.

In Pugh v. United States, the Supreme Court was asked to decide whether a federal statute that imposed an additional tax on certain distilled spirits was constitutional. The majority of justices held that Congress had the power to impose such taxes under its authority granted by Article I, Section 8 of the Constitution and therefore found in favor of the government. Justice Field dissented from this opinion, arguing that while Congress did have broad powers over taxation, it could not use them as a means for raising revenue without regard for other provisions in the Constitution or laws passed by state legislatures. He argued further that if Congress were allowed to do so then it would be able to override any law made by states with respect to their own internal affairs and thus violate principles enshrined in both state sovereignty and separation of powers between branches of government at all levels.