Ex parte Jordan was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner who was being held in federal custody. The case arose when a prisoner, John Jordan, was arrested by federal authorities in the state of Texas and held in federal custody. Jordan then filed a petition for a writ of habeas corpus in a state court, arguing that he was being held in violation of his constitutional rights. 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 the writ of habeas corpus, as the federal government had exclusive jurisdiction over the matter. 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. The Court also noted that the writ of habeas corpus was a remedy that could only be used in cases where the prisoner was being held in violation of his constitutional rights, and that the state court had no authority to determine whether or not the prisoner's rights had been violated. In conclusion, the Supreme Court held that the state court did not have the authority to issue the writ of habeas corpus to a prisoner being held in federal custody. 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.

In Ex Parte Jordan, the Supreme Court was asked to decide whether a writ of habeas corpus should be issued in order for an individual to challenge his or her detention. The majority opinion held that the writ should not issue because it would interfere with the power of Congress and state legislatures to regulate immigration. Justice Field dissented from this decision, arguing that individuals have a right under the Constitution to challenge their detention through habeas corpus proceedings. He argued that while Congress has authority over immigration matters, they do not have unlimited powers and must respect constitutional rights when making decisions about such matters. Furthermore, he noted that if individuals were denied access to habeas corpus proceedings then they could be unlawfully detained without any recourse for challenging their imprisonment. As such, Justice Field concluded by stating that denying access to these proceedings violated fundamental principles of justice and due process guaranteed by both federal law and international treaties ratified by Congress.