In the ex parte milligan case, the u. s. supreme court stated that:

a. milligan should be hanged for writing pro-confederate editorials during the civil war.
b. secession was unconstitutional. accused persons must be tried before civil courts where there were open, rather than military, tribunals.
c. a president could order the jailing of civilians for any reason whatsoever during wartime.
d. congress, not the president, has the power to suspend the writ of habeas corpus.

The answer is b): secession was unconstitutional. accused persons must be tried before civil courts where there were open, rather than military, tribunals.

Explanation:

In 1864, Lambdin P. Milligan was arrested and charged with helping the Confederacy to incite an uprising against the U.S. government, and conspiring to free Confederate prisoners. Milligan was tried by a military court set up in Indiana by President Lincoln, and sentenced to hanging. However, Milligan’s lawyers sought a writ of habeas corpus and challenged the constitutionality of Milligan’s trial in a military court. When the case finally reached the Supreme Court, the Supreme Court unanimously declared that President Abraham Lincoln lacked the constitutional power to create military courts in areas where secure civil courts were already functioning: accused persons should be tried in civil courts, wherever they exist, rather than in military courts. On the other hand, it was unconstitutional for any group (for example, the Confederacy) to secede or remove a state from the authority of the Union that constitutes the United States of America.