United States v. Smoot was a United States Supreme Court case that dealt with the issue of whether a federal court had the power to issue a writ of habeas corpus to a state prisoner. The case arose when a prisoner, William Smoot, was arrested in the District of Columbia and charged with a crime in the state of Virginia. Smoot sought a writ of habeas corpus from the federal court in the District of Columbia, arguing that he was being held in violation of the Constitution. The Supreme Court held that the federal court did not have the power to issue a writ of habeas corpus to a state prisoner. The Court reasoned that the writ of habeas corpus was a remedy for federal prisoners, and that the federal court did not have the power to interfere with the state's criminal justice system. The Court also noted that the writ of habeas corpus was a remedy for federal prisoners, and that the federal court did not have the power to interfere with the state's criminal justice system. The Court's decision in United States v. Smoot established that the federal court did not have the power to issue a writ of habeas corpus to a state prisoner. This decision has been cited in numerous cases since then, and it has been used to support the principle that the federal court should not interfere with the state's criminal justice system.

In United States v. Smoot, the Supreme Court was tasked with determining whether a federal court had jurisdiction to try an individual for violating a state law. The majority opinion held that it did not have such authority and dismissed the case. Justice Field dissented from this decision, arguing that Congress has the power to pass laws which are applicable in all states and territories of the United States, including those regarding criminal matters. He argued further that if Congress could pass laws concerning civil matters within these areas then they should also be able to do so when it comes to criminal cases as well. He concluded by stating that while he agreed with much of what was said in the majority opinion, he felt strongly enough about his position on this matter to dissent from their ruling.