In Flagg & Another v. Walker, the Supreme Court of the United States was asked to decide whether a state court had the authority to issue a writ of habeas corpus to a prisoner who had been convicted in a federal court. The case arose when two prisoners, Flagg and Walker, were convicted in a federal court in the District of Columbia and sentenced to imprisonment. The prisoners then sought a writ of habeas corpus from the Supreme Court of the District of Columbia, which was denied. The prisoners then sought a writ of habeas corpus from the Supreme Court of the United States, which was also denied. The Supreme Court held that the state court did not have the authority to issue a writ of habeas corpus to a prisoner who had been convicted in a federal court. The Court reasoned that the writ of habeas corpus was a remedy available only to prisoners who had been convicted in a state court, and that the federal court had exclusive jurisdiction over the prisoners in this case. The Court also noted that the writ of habeas corpus was a remedy available only to prisoners who had been convicted in a state court, and that the federal court had exclusive jurisdiction over the prisoners in this case. The Court concluded that the state court did not have the authority to issue a writ of habeas corpus to a prisoner who had been convicted in a federal court. The Court held that the writ of habeas corpus was a remedy available only to prisoners who had been convicted in a state court, and that the federal court had exclusive jurisdiction over the prisoners in this case.

In Flagg & Another v. Walker, the Supreme Court was asked to decide whether a judgment of foreclosure and sale in favor of one party could be set aside on the grounds that it had been procured by fraud or collusion between the parties. The majority opinion held that such a judgment could not be set aside unless there were clear proof of fraud or collusion, which did not exist in this case. Justice Field dissented from this decision, arguing that courts should have more discretion when considering cases involving allegations of fraud or collusion. He argued that if an allegation is made and supported with sufficient evidence, then courts should consider setting aside judgments even without clear proof of wrongdoing because allowing them to stand would encourage fraudulent behavior among litigants who are aware they can get away with it due to lack of oversight from the court system.