Ex parte Karstendick 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, Karstendick, was held in a federal prison in Wisconsin. Karstendick sought a writ of habeas corpus from the Wisconsin state court, claiming that he was being held in violation of his constitutional rights. The federal government argued that the state court did not have the authority to issue the writ, as the prisoner was being held in a federal prison. 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 remedy, 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 remedy that could only be used to challenge the legality of a prisoner's detention, and not to challenge the conditions of the prisoner's confinement. As such, the Court held that the state court did not have the authority to issue the writ of habeas corpus.

In Ex Parte Karstendick, the Supreme Court was asked to decide whether a state court had jurisdiction over an action brought by a non-resident against another non-resident. The majority opinion held that the state court did not have jurisdiction in this case because both parties were from different states and there was no connection between them or their dispute with the forum state. Justice Field dissented, arguing that it is within the power of each State to determine who may bring suit in its courts and what matters can be litigated therein. He argued that since neither party resided in nor had any business connections with California (the forum state), then they should not be allowed to sue one another there; however, he also noted that if either party voluntarily appeared before the court without objection then they could waive their right to challenge personal jurisdiction. Ultimately, Justice Field concluded that while it would have been better for Congress or individual States to pass laws regulating such cases involving out-of-state parties suing each other in foreign jurisdictions, absent such legislation he believed it was up to each State's discretion as long as due process rights were respected.