Ex parte Easton 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 held in federal custody. The case arose when a prisoner, Easton, was held in federal custody in the state of California. Easton sought a writ of habeas corpus from the state court, claiming that he was being held in violation of the Constitution. The state court granted the writ, and Easton was released from federal custody. The United States 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 detain a prisoner. 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 a writ of habeas corpus to a prisoner held in federal custody. 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 Easton, 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 because it lacked personal service of process on both parties and therefore could not exercise its authority in this case. Justice Field dissented from this decision, arguing that due process requires only reasonable notice of proceedings and does not require personal service of process for all cases involving non-residents. He argued that if there is sufficient evidence to show that one party has received actual or constructive notice of the proceedings then they should be bound by them regardless of whether they were personally served with papers or not. Furthermore, he noted that courts must take into account public policy considerations when deciding such matters as well as practicality since it would be impossible for out-of-state defendants to appear in person at every trial where their presence is required. Therefore, Justice Field concluded his dissent by stating his belief that due process can still be satisfied without requiring strict compliance with formalities like personal service in all cases involving out-of-state defendants.