Ex parte Robinson was a United States Supreme Court case that dealt with the issue of habeas corpus. The case involved a man named William Robinson, who was arrested and held in custody without a warrant. Robinson filed a petition for a writ of habeas corpus, which is a legal document that requires a person to be brought before a court to determine if they are being held lawfully. The Supreme Court ruled that the writ of habeas corpus was not available to Robinson because he was not being held in custody by a state or federal court. The Court held that the writ of habeas corpus was only available to those who were being held in custody by a court. The Court also held that the writ of habeas corpus was not available to those who were being held in custody by a private individual or corporation. This ruling established the precedent that the writ of habeas corpus is only available to those who are being held in custody by a court.

In Ex Parte Robinson, the Supreme Court was asked to decide whether a writ of habeas corpus should be granted in order for an individual to be released from prison. The majority opinion held that the writ should not be issued because it would interfere with state proceedings and undermine public confidence in judicial decisions. Justice Field dissented, arguing that the writ of habeas corpus is a fundamental right guaranteed by both federal and state constitutions which cannot be denied without due process of law. He further argued that since no criminal trial had been conducted or sentence imposed on Robinson, he could not have received due process before being imprisoned and thus his imprisonment was unlawful. Furthermore, Field stated that if states were allowed to imprison individuals without providing them with their constitutional rights then those same rights would become meaningless as they could easily be taken away at any time by any government authority.