ex parte Milligan (1866)
A person sentenced to death for disloyalty by a military court had the right to appeal his case in a civil court, as long as civil courts were operational. The Court noted the government’s power to suspend habeas corpus in rebellion or invasion, but pointed out that the citizens’ Sixth Amendment right to trial by jury was preserved. The Framers knew that “trial by an established court, assisted by an impartial jury, was the only sure way of protecting the citizen against oppression and wrong. Knowing this, they limited the suspension to one great right [habeas corpus], and left the rest to remain forever inviolable.”
The ruling also defined conditions for martial law and asserted civilian power over the military. “Martial law cannot arise from a threatened invasion. The necessity must be actual and present; the invasion real, such as effectually closes the courts and deposes the civil administration…As necessity creates the rule, so it limits its duration; for, if this government is continued after the courts are reinstated, it is a gross usurpation of power. Martial rule can never exist where the courts are open, and in the proper and unobstructed exercise of their jurisdiction. It is also confined to the locality of actual war.”
The case touched on constitutional principles including separation of powers, checks and balances, and individual rights, and civic values including justice.