Ex parte Milligan, 71 U.S. 2 (1866), was a United States Supreme Court case that ruled that the application of military tribunals to citizens when civilian courts are still operating is unconstitutional.
Background of the case
Lambdin P. Milligan and four others were accused of planning to steal Union weapons and invade Union prisoner-of-war camps. Once the first prisoner of war camp was liberated they planned to use the liberated soldiers to help fight against the Government of Indiana and free other camps of Confederate soldiers. They also planned to take over the state governments of Indiana, Ohio, and Michigan. When the plan leaked, they were charged, found guilty, and sentenced to hang by a military court in 1864. However, their execution was not set until May 1865, so they were able to argue the case after the Civil War ended.
The argument for the United States was delivered by Benjamin F. Butler, a Massachusetts lawyer and state legislator, and future Governor of Massachusetts.
The argument for the petitioner was delivered by Jeremiah S. Black, former Attorney General and Secretary of State, James A. Garfield, future President, and New York lawyer David Dudley Field.
The Supreme Court's Decision
The Supreme Court decided that the suspension of habeas corpus was lawful, but military tribunals did not apply to citizens in states that had upheld the authority of the Constitution and where civilian courts were still operating, and the Constitution of the United States provided for suspension of habeas corpus only if these courts are actually forced closed. In essence, the Court ruled that military tribunals could not try civilians in areas where civil courts were open, even during times of war.
It observed further that during the suspension of the writ of habeas corpus, citizens may be only held without charges, not tried, and certainly not executed by military tribunals. After all, the writ of habeas corpus is not the right itsel...