Well then,
Under the Constitution the federal government can unquestionably suspend the privilege of the writ of
habeas corpus if the public safety requires it during times of rebellion or invasion.
Historical perspective on that issue in the context of the Civil War requires a study of the actions of Congress and the president, Lincoln's defense of his suspensions of the writ, and presidential and congressional dealings with and reactions to each other.
The background is well known. After Virginia seceded from the Union on April 17, 1861, the only lines for overland supplies, troop movements, transportation, and communication to Washington, D.C., ran through Maryland, with the railroads running through Baltimore.
Baltimore was a rough city for the Union, and Maryland an uncertain ally.
In February, Baltimore rowdies had forced President-elect Lincoln to sneak through the city in disguise, and a mob attacked the Sixth Massachusetts Regiment as it marched through Baltimore on its way to Washington.
Confederate sympathizers in Maryland were numerous, organized, and sometimes violent.
The Maryland legislature was of questionable loyalty, prompting Lincoln to monitor its April 26 session and, later, to order the arrest of a number of its members.
Determined to keep the Maryland lines open, on April 27 Lincoln issued an order to General Winfield Scott authorizing him to suspend the writ of
habeas corpus, at or near any military line between Philadelphia and Washington if the public safety required it.
Lincoln issued his order pursuant to the provision in Article I, Section 9 of the Constitution stating that "the privilege of the writ of
habeas corpus shall not be suspended, unless when in cases of rebellion and invasion the public safety may require it," generally called the suspension clause.
http://quod.lib.umich.edu/j/jala/2629860.0029.205?rgn=main;view=fulltext
