Walker v. Sauvinet was a United States Supreme Court case that addressed the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner held in federal custody. The case arose when a prisoner, Walker, was held in federal custody in Louisiana. Walker sought a writ of habeas corpus from the state court, which the court granted. The United States government then 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 federal custody. The Court reasoned that the writ of habeas corpus was a federal prerogative, and that the state court did not have the authority to interfere with the federal government's power to detain a prisoner. 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 federal custody. The Court reasoned that the writ of habeas corpus was a federal prerogative, and that the state court did not have the authority to interfere with the federal government's power to detain a prisoner.

In Walker v. Sauvinet, the United States Supreme Court was tasked with determining whether a Louisiana state court had jurisdiction to hear an appeal from a decision of the Circuit Court for the Parish of Orleans in a case involving real property located in New Orleans. The majority opinion held that it did not have such jurisdiction because under Louisiana law at the time, appeals were only allowed when there was no dispute as to title or possession of land and this case involved both. Justice Field dissented on behalf of himself and two other justices, arguing that while he agreed with much of what was stated by Chief Justice Waite's majority opinion, he disagreed with its conclusion regarding lack of appellate jurisdiction due to disputes over title or possession. He argued that if this were true then any judgment rendered by a lower court would be final regardless if it contained errors which could lead to injustice being done without recourse for relief through an appeal process. Therefore, according to Justice Field's dissent, even though there may have been some ambiguity in how Louisiana law should be interpreted on this issue at the time; ultimately it should be construed so as not deny litigants their right to seek redress through an appellate process whenever possible