Ex parte Ralston is 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, Ralston, was held in a federal prison in California and sought a writ of habeas corpus from the state court. The state court granted the writ and ordered the federal prison to release Ralston. The federal government appealed the decision to the Supreme Court, arguing that the state court did not have the authority to issue the writ. 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 is a federal remedy and that the state court did not have the power to interfere with the federal government's authority to imprison individuals. The Court also noted that the writ of habeas corpus is a remedy that is available only to individuals who are being held in state custody, not federal custody. The Court's decision in Ex parte Ralston established that state courts do not have the authority to issue writs of habeas corpus to individuals who are being held in federal custody. This decision has been cited in numerous subsequent cases and has become an important precedent in the area of federal-state relations.

In Ex Parte Ralston, the United States Supreme Court was asked to determine whether a state court had jurisdiction over an action brought by one of its citizens against another citizen who resided in a different state. The majority opinion held that the state court did not have jurisdiction because it lacked personal service on the defendant and therefore could not exercise power over him. Justice Field dissented from this decision, arguing that due process requires only reasonable notice of suit and does not require personal service for out-of-state defendants. He argued that if states are allowed to refuse suits based solely on lack of personal service, then they will be able to deny justice without any real cause or justification. Furthermore, he noted that there is no constitutional requirement for such strict rules regarding out-of-state defendants as long as they receive sufficient notice about their case so they can make arrangements to defend themselves adequately in court. Thus, Justice Field concluded that due process should protect all parties regardless of where they reside and allow them access to justice through proper notification rather than requiring strict adherence to technicalities like personal service requirements which may prevent individuals from receiving fair treatment under law.