Ex parte Reggel 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 a federal prison. The case arose when a prisoner, Reggel, was held in a federal prison in Texas and sought a writ of habeas corpus from a state court. The state court granted the writ and ordered the federal prison to release Reggel. 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 the writ of habeas corpus. The Court reasoned that the writ of habeas corpus was a federal power and that the state court did not have the authority to interfere with the federal government's power to imprison individuals. The Court also noted that the writ of habeas corpus was a fundamental right and that the state court should not 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 the writ of habeas corpus to a prisoner held in a federal prison. The Court reasoned that the writ of habeas corpus was a federal power and that the state court should not interfere with the federal government's power to protect this fundamental right.

In Ex Parte Reggel, the Supreme Court was asked to decide whether a state court had jurisdiction over a case involving an alleged breach of contract between two citizens of different states. The majority opinion held that the state court did have jurisdiction because it involved matters arising under local law and not federal law. However, Justice Field dissented from this decision on the grounds that there were no facts in dispute and thus no need for judicial determination by either a state or federal court. He argued that since both parties were citizens of different states, any controversy should be decided by a federal tribunal as provided for in Article III Section 2 of the Constitution. Furthermore, he noted that even if there was some issue requiring judicial resolution, such issues could still be determined without resorting to litigation in either forum due to principles established by prior decisions regarding diversity cases. Ultimately Justice Field concluded that allowing one party's suit against another citizen from another state would open up too many avenues for potential abuse and therefore should not be allowed unless absolutely necessary according to constitutional requirements