Phelps v. McDonald was a United States Supreme Court case that addressed the issue of whether a state court could issue a writ of habeas corpus to a prisoner who was being held in a federal prison. The case arose when a prisoner, McDonald, was held in a federal prison in the state of New York. McDonald 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 for violations of the Constitution, and that the state court did not have the power to determine whether the federal government had violated the Constitution. The Court's decision in Phelps v. McDonald established that state courts do not have the authority to issue writs of habeas corpus to prisoners held in federal prisons. The decision also established that the writ of habeas corpus is a federal remedy, and that state courts do not have the power to determine whether the federal government has violated the Constitution.

Justice Field delivered the dissenting opinion in Phelps v. McDonald, arguing that a judgment of foreclosure should not be reversed on appeal due to an alleged irregularity in the proceedings leading up to it. He argued that if there was any error or irregularity during those proceedings, then it could have been corrected by motion for rehearing before the court rendered its decision and thus should not be considered as grounds for reversal on appeal. Furthermore, he noted that even if such irregularities had occurred they would only affect the validity of certain parts of the decree and not necessarily invalidate all aspects of it; therefore, reversing a judgment based solely on these issues would be inappropriate. Justice Field concluded his dissent by noting that while courts must always ensure justice is done when considering appeals from judgments like this one, they must also take care to avoid overturning them without good cause since doing so can lead to unnecessary delays and expense for both parties involved in litigation.