Ex Parte Milligan — Civil Liberties in Wartime

Ex Parte Milligan, 71 U.S. (4 Wall.) 2 (1866), is one of the Supreme Court's most important decisions about the limits of military power over civilians in wartime — and one of the most eloquent defenses of the principle that the Constitution does not stop at the battlefield. Lambdin P. Milligan, a civilian Indiana lawyer who opposed the Civil War, was arrested by military authorities in 1864 for allegedly conspiring to liberate Confederate prisoners and lead an armed insurrection. He was tried by a military commission, convicted, and sentenced to hang — despite the fact that civil courts were open and functioning in Indiana throughout the war. The Supreme Court held unanimously that Milligan's military trial was unconstitutional: civilians who are not members of the armed forces, who reside in states where civil courts are open, cannot be tried by military tribunal even during wartime. Only Congress's formal suspension of the writ of habeas corpus — and even then, only where civilian courts have been displaced by actual warfare — can justify trying civilians before military commissions. Milligan is cited in every major national security case involving military detention or trial of civilians — including Hamdi v. Rumsfeld (2004) and Boumediene v. Bush (2008) — and represents the constitutional principle that "the Constitution of the United States is a law for rulers and people, equally in war and in peace."

Current Law (2026)

Legal Authority

• U.S. Const. art. I, § 9, cl. 2 — Suspension Clause: "The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it" — the constitutional authorization for emergency military detention; Milligan defined its limits
• U.S. Const. amend. V — Due Process Clause: "No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger" — the exception for military personnel; civilians fall outside it
• U.S. Const. amend. VI — Right to jury trial in criminal prosecutions; military commissions deny this right
• 28 U.S.C. § 2241 — Federal habeas corpus statute; the mechanism Milligan used; still the primary vehicle for challenging unlawful detention
• 10 U.S.C. § 948a et seq. — Military Commissions Act: the modern statutory framework for military commissions at Guantanamo; expressly limited to "alien unprivileged enemy combatants" — consistent with Milligan's holding that U.S. citizens in loyal states cannot be tried militarily
• Ex Parte Vallandigham, 68 U.S. 243 (1864) — Earlier Civil War case where the Court declined to exercise jurisdiction over a military commission trial of a civilian; Milligan effectively overruled Vallandigham's implicit acceptance of military jurisdiction over civilians
• Korematsu v. United States, 323 U.S. 214 (1944) — Japanese American exclusion upheld; Justice Murphy's dissent cited Milligan; Korematsu formally repudiated in Trump v. Hawaii (2018)
• Hamdi v. Rumsfeld, 542 U.S. 507 (2004) — Enemy combatant due process; plurality cited Milligan; plurality distinguished Milligan because Hamdi was captured on a foreign battlefield, not a civilian in a loyal state

Key Mechanics

Ex parte Milligan, 71 U.S. (4 Wall.) 2 (1866), held that military tribunals cannot try civilians when civilian courts are open and functioning, even during wartime. The core rule: the Constitution's guarantees (grand jury indictment, trial by jury) apply to civilians in non-combat zones where civilian courts are operating. The federal government cannot suspend these guarantees by simply declaring a military emergency; only Congress can suspend habeas corpus (Art. I § 9), and even that suspension does not permit military trials of civilians in jurisdictions with functioning federal courts. The decision drew a critical distinction between the "theater of active military operations" (where military jurisdiction is appropriate) and the loyal states behind the lines (where civilian courts remain open) — Milligan was in Indiana, not a Confederate state. Milligan has been limited by subsequent decisions (Quirin (1942), Hamdi (2004)) but has never been overruled.

How It Works

Lambdin Milligan and the Indiana Conspiracy

Lambdin P. Milligan was a prominent Indiana lawyer and anti-war Democrat — a "Copperhead" in Civil War parlance — who vigorously opposed the Lincoln administration's conduct of the war. In the fall of 1864, as Union victory appeared increasingly likely, military authorities arrested Milligan and several other Indiana civilians, charging them with conspiring to steal weapons, liberate Confederate prisoners, and launch an armed uprising against the Union government.

Milligan was not a soldier. He was never affiliated with the Confederate military. He lived in Huntington, Indiana, where the civil courts of the United States were open and functioning throughout the entire period — there was no actual warfare in Indiana, no occupied territory, and no impediment to civilian prosecution. Despite this, Milligan was tried before a military commission, convicted, and sentenced to hang.

President Lincoln was assassinated before the sentence could be carried out; President Johnson initially declined to intervene. Milligan's lawyers filed a petition for habeas corpus in federal circuit court, arguing the military commission lacked jurisdiction. The circuit court certified the questions to the Supreme Court.

The Supreme Court's Ruling

Justice Davis's majority opinion (for five justices) held that Milligan's military trial was unconstitutional and that he was entitled to release. The holding rested on two foundations:

First — The constitutional text: The Fifth Amendment explicitly carves out an exception to the grand jury requirement "in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger." This exception, by its terms, applies only to members of the military forces. Milligan was a civilian; he was not a member of the land or naval forces. The exception did not apply to him, and therefore the full Fifth Amendment right to grand jury indictment applied. A military commission — which conducts no grand jury proceeding — could not substitute for civil trial.

Second — The open courts principle: Military jurisdiction over civilians is constitutionally permissible only in two circumstances: (1) where the individual is a member of the military, or (2) where civilian courts have been displaced by actual military occupation or warfare — where the civil courts are "closed." In Indiana during the Civil War, the civil courts were open and functioning. There was no military occupation, no displacement of civilian authority, and no operational necessity that precluded civilian prosecution. In such circumstances, civilian courts have exclusive jurisdiction over civilians:

"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. Because, during the late Rebellion it could have been enforced in Virginia, where the national authority was overturned and the courts driven out, it does not follow that it should obtain in Indiana, where that authority was never disputed, and justice was always administered."

The majority went further: even Congress could not authorize military trials of civilians in loyal states where courts are open. Military jurisdiction over civilians is constitutionally limited, not merely a matter of congressional discretion.

The Chase Minority: Congressional Authorization

Chief Justice Chase (for four justices) concurred in the result — Milligan's conviction was invalid — but disagreed with the majority's reasoning on Congress's power. Chase argued that Congress could constitutionally authorize military trials of civilians during wartime if it chose to; the problem in Milligan's case was that Congress had not in fact done so. The existing federal statutes governing military commissions did not authorize trial of civilians in Milligan's circumstances.

This disagreement has practical importance: the majority's categorical rule (Congress cannot authorize civilian military trials where civil courts are open) is broader and more protective than Chase's rule (Congress could authorize such trials but hadn't). The majority's view prevailed and is the holding Milligan stands for today.

Milligan's Scope: Who It Protects and Who It Doesn't

Milligan is sometimes over-read. Its holding is specifically about civilians in loyal states where civil courts are open and functioning. It does not resolve:

Enemy combatants: The Milligan majority distinguished between "citizens who are prisoners of war" and civilians who simply oppose the government. An enemy combatant — someone who takes up arms against the United States — has different status than a civilian dissenter. Hamdi v. Rumsfeld (2004) held that Milligan did not protect Yaser Hamdi, a U.S. citizen captured fighting with the Taliban in Afghanistan, because he was captured in active combat operations, not arrested as a civilian in a loyal state.

Occupied territory: Where actual military occupation has displaced civilian courts — as in Confederate Virginia during the Civil War, or occupied Japan and Germany after World War II — military jurisdiction over civilians may be permissible because the condition Milligan requires (open civil courts) is not met.

Military personnel: Milligan has no effect on military justice for service members. The Uniform Code of Military Justice (UCMJ) governs military personnel through courts-martial — a constitutionally authorized military tribunal system. The Fifth Amendment's exception for military forces explicitly permits this.

Foreign nationals: Milligan protects American citizens in loyal states; it does not directly address the constitutional status of foreign nationals captured abroad. Boumediene v. Bush (2008) extended habeas corpus to Guantanamo detainees on different grounds (the Suspension Clause's geographic reach), and Milligan was relevant context but not directly controlling.

Milligan's Legacy: The Constitution in Wartime

Milligan's enduring contribution is the principle that the Constitution's protections do not evaporate in wartime — that emergency does not suspend constitutional rights except through the specifically authorized mechanism of habeas suspension by Congress, and even then only where courts are actually displaced. The decision was a deliberate rebuke to the Lincoln administration's wartime practices (though Lincoln was dead when the decision was issued), and it established a constitutional norm that emergency claims do not justify abandoning constitutional structure.

This principle has been invoked (and contested) in every major national security crisis since: the Japanese American internment (where the principle was violated, as Korematsu's eventual repudiation acknowledges), the post-9/11 detention regime (where Hamdi and Boumediene vindicated the spirit of Milligan), and ongoing debates about surveillance, detention, and military authority.

How It Affects You

If you are an American civilian being held by military authorities: Milligan establishes that you cannot be tried by military commission if you are a civilian residing in the United States where civil courts are functioning. If you have been detained by military authorities and denied access to civilian courts, you have the constitutional right to petition for a writ of habeas corpus in federal district court under 28 U.S.C. § 2241. A federal court must determine whether the conditions for military jurisdiction are met — whether you are a member of the military or captured on a battlefield — and must release you to civilian courts if those conditions are not satisfied. The Non-Detention Act (50 U.S.C. § 4001) separately requires that any detention of a U.S. citizen must be authorized by an Act of Congress. Contact an attorney with national security or habeas corpus experience immediately.

If you are a national security or military attorney advising on detention authority: Milligan draws the constitutional line for military jurisdiction over U.S. civilians: if civil courts are open and the person is not a battlefield combatant or military member, military tribunal jurisdiction is unconstitutional — full stop, even if Congress tries to authorize it (under the majority view). The battlefield capture exception (Hamdi) requires actual capture in armed conflict; the mere fact that a citizen sympathizes with or assists enemy forces in a country where courts are open does not by itself create military jurisdiction. Civilian prosecution is constitutionally required in such cases. Military commissions at Guantanamo are permissible for "alien unprivileged enemy combatants" under the Military Commissions Act — consistent with Milligan because these are foreign nationals captured in combat, not U.S. civilians in loyal states.

If you are a civil liberties advocate or constitutional historian: Milligan is the foundational principle that the Constitution operates as a limit on emergency power — that "necessity" does not create its own constitutional authority. This principle has been honored more in breach than in observance during actual wartime emergencies, but it has been consistently reaffirmed as the constitutional baseline when the immediate crisis has passed. The trajectory from Milligan (1866) to Korematsu (1944, later repudiated) to Hamdi and Boumediene (2004, 2008) traces the Supreme Court's recurring struggle to maintain constitutional limits under national security pressure. Milligan's specific holding — civilian courts remain open, military cannot try civilians — has held up; the broader principle that the Constitution limits wartime emergency power remains contested in each generation.

If you are a policy maker or legislator addressing national security law: Milligan establishes that certain uses of military power against civilians are beyond even congressional authorization — the majority's view that military trial of civilians where courts are open exceeds even legislative authority is a constitutional constraint on what national security legislation can accomplish. The proper response to civilian threats is civilian prosecution: federal criminal law addressing terrorism (18 U.S.C. § 2331 et seq.), conspiracy, weapons offenses, and material support for terrorism provides comprehensive authority for civilian prosecution of civilian defendants. Military commissions are for captured battlefield combatants — the category Milligan expressly excluded from its protection.

State Variations

Milligan operates at the federal constitutional level; it defines the limits of federal military power over civilians. State law cannot expand federal military jurisdiction beyond what Milligan permits. However, several state-level dimensions are relevant:

State criminal prosecution: Milligan's specific holding protects against military trial; it says nothing about state criminal prosecution. Persons who engage in activities threatening national security — but who are civilians residing in loyal states — can and should be prosecuted in state courts (for state crimes) or federal courts (for federal crimes). State courts remain open and constitutionally required.

State emergency powers and martial law: Governors have emergency powers under state constitutions and statutes, including in some cases authority to declare martial law. State martial law declarations historically involved deploying the National Guard for law enforcement; they do not confer military tribunal jurisdiction over civilians in states where civil courts are functioning. Milligan's principle applies to state executive power through the Fourteenth Amendment's due process clause.

State National Guard: National Guard members, when in federal active service, are "militia in actual service" for purposes of the Fifth Amendment's military exception — they can be tried by military courts-martial. When serving exclusively under state authority as members of the organized militia, their legal status is governed by state law and the Posse Comitatus Act's restrictions on using military force for domestic law enforcement.

Pending Legislation

Milligan's holding is so fundamental that no pending legislation directly challenges it. Ongoing legislative debates implicate its principles:

• Military Commissions Act and Guantanamo: The MCA specifically limits military commission jurisdiction to "alien unprivileged enemy combatants" — consistent with Milligan by excluding U.S. civilians from military jurisdiction. Proposals to modify MCA procedures continue to generate debate, but none propose extending military commission jurisdiction to U.S. civilians.
• Domestic terrorism and surveillance: Proposals to create new categories of domestic terrorist designation, enhance surveillance authority, or expand material support prohibitions implicate Milligan's principle that civilian threats require civilian prosecution. Milligan forecloses — constitutionally and categorically — proposals that would permit military trial of U.S. civilian terrorism suspects in states where courts are open.

Recent Developments

• 2004 — Hamdi v. Rumsfeld: The Supreme Court cited Milligan while distinguishing it — Yaser Hamdi was captured fighting with the Taliban in Afghanistan, not a civilian dissenter in a loyal state. The plurality upheld detention authority while requiring due process; Milligan provided the outer limit framework.
• 2006 — Hamdan v. Rumsfeld: The Court struck down the original Guantanamo military commissions partly because they violated the UCMJ and the Geneva Conventions; Milligan principles informed the analysis. Congress responded with the Military Commissions Act.
• 2008 — Boumediene v. Bush: Guantanamo detainees have constitutional habeas corpus rights; Milligan's principle that judicial review remains available even in national security emergencies was reaffirmed and extended to foreign nationals at Guantanamo.
• 2018 — Trump v. Hawaii: Korematsu formally repudiated — the Japanese internment decision, which violated Milligan's principle that civilian courts remain open in loyal states, was overruled in the court of history and now explicitly in Supreme Court dicta.
• 2025 — Domestic terrorism prosecution: The Trump administration's prosecution of January 6th defendants in civilian courts (not military commissions) — even those accused of serious violence — illustrates that Milligan's framework governs domestic threats: civilian prosecution, not military jurisdiction. Proposals to designate certain domestic actors as enemy combatants subject to military detention face Milligan's constitutional barrier.