Walker v. Powers 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 the state of New York. Walker sought a writ of habeas corpus from the state court, which the court granted. The federal 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.

Justice Field delivered the dissenting opinion in Walker v. Powers, arguing that the majority's decision was incorrect and should be reversed. He argued that a contract between two parties is binding on both of them, regardless of any subsequent changes to state laws or regulations. In this case, he noted that there had been an agreement between Walker and Powers for the sale of certain real estate which included specific terms regarding payment by installments over time. The state legislature then passed a law requiring all such contracts to include additional provisions related to foreclosure proceedings if payments were not made as agreed upon; however, these new requirements did not apply retroactively to existing contracts like those at issue here since they would have altered their original terms without either party's consent or knowledge. Justice Field concluded his dissent by stating that it was improper for courts to interfere with private contractual arrangements unless there has been fraud or other misconduct involved in making them; thus, he believed the lower court’s ruling should stand and be affirmed rather than overturned as done by the majority opinion in this case.