Written by attorneys · grounded in primary & secondary sources — see below
A constitutional limitation that bars Congress from authorizing military courts to try American civilians when civilian courts remain open and functioning, even during declared emergencies or martial law. The limitation protects Fifth and Sixth Amendment jury-trial rights by confining military jurisdiction to members of the armed forces and true battlefield conditions.
Sources & Authorities
How it applies
Common Examples
6
Civilian Farmer Tried by Base Commander
After a suspected bioweapon incident near Fort Calhoun, Colonel Reeves imposed curfews and arrested Miguel Diaz, owner of Diaz Family Farms LLC, for alleged sabotage. Reeves convened a court-martial that convicted Diaz even though state and federal civilian courts in the region stayed open with only minor delays. Diaz petitions for habeas corpus. The district court must grant relief because the military tribunal lacked authority over a civilian while ordinary courts remained operational.
Nurse Arrested at Hospital Zone
Active-duty military police arrested Elena, a civilian nurse employed by MedCore Health Systems, after a bioterror scare at Metropolitan General. A military prosecution unit declared the hospital a temporary military zone and scheduled a court-martial while the nearby federal courthouse continued to conduct trials. Elena seeks an injunction. The federal district court must enjoin the proceeding because Elena remains a civilian entitled to trial in an open Article III court.
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Cases
Dictionaries
Stevedore Charged at Declared Port
During a surge in shipping threats, the President declared Harbor City's port a military security zone. Naval authorities arrested Daniel Reed, a civilian stevedore for Atlantic Lift Services, for alleged weapons smuggling and ordered a court-martial. The nearby federal district court remained fully open and hearing maritime cases. Reed challenges the tribunal. The court must hold the military proceeding unconstitutional because civilian courts capable of trying the case stayed operational.
Engineer Detained at Aerospace Plant
Air Force personnel stationed at Pacific Jet's private plant arrested Sabrina, a civilian avionics engineer, for allegedly embedding malicious code in navigation systems. Military authorities scheduled a commission despite the federal district court in State A remaining fully open and handling national-security cases. Sabrina petitions to enjoin the proceeding. The district court must grant relief because her civilian status and the functioning civilian court bar military jurisdiction.
Consultant Held After Pipeline Attacks
Troops guarding environmental sites arrested Hugh, an American civilian consultant for Sun Earth, on suspicion of coordinating eco-sabotage. The Department of Education declared an emergency and directed a court-martial even though State A criminal courts and federal district courts stayed fully operational. Hugh seeks to enjoin the military trial. The federal court must order transfer to civilian court because the open civilian forums preclude military adjudication of a civilian.
Retail Clerk Facing Military Tribunal
Active-duty troops assisting local police arrested Warren, a civilian clerk for Crown Retail, during looting in State O's downtown district. The joint task force scheduled a temporary military tribunal at an armory while the State O courthouse and adjacent federal district court remained open and accepting filings. Warren petitions for habeas corpus. The district court must grant relief because the functioning civilian courts deprive the military tribunal of authority over the civilian.
Common questions
Frequently Asked
3
When may the military try a civilian by court-martial during an emergency?+
The military may not try a civilian by court-martial when civilian courts remain open and functioning. The Constitution limits military jurisdiction over civilians to true battlefield conditions or when civil courts are closed. Emergency declarations or national-security concerns do not override this limit.
Does a declaration of martial law allow military trials of civilians?+
No. A declaration of martial law does not suspend jury-trial protections when civilian courts stay open. The controlling test is whether ordinary courts remain available and capable of functioning, not whether an emergency has been declared.
What happens if a civilian is convicted by an unauthorized military tribunal?+
The conviction is void for lack of jurisdiction. A federal court may grant habeas corpus or an injunction because the military tribunal had no constitutional power to try the civilian while civilian courts operated.
369 U.S. 186, 211Constitutional Law
…action on the ground that they were agents of the established lawful government of Rhode Island, which State was then under martial law to defend itself from active insurrection; that the plaintiff was engaged in that insurrection; and that they entered under orders to arrest the plaintiff. The case arose "out of the…