Lincoln’s orders on habeas corpus (excerpts)
In hopes of reducing tensions in Maryland in April 1861, Lincoln resisted military advice to arrest secessionist Maryland legislators before they met, but on April 25 he instructed Winfield Scott, the commanding general of the Army, to watch the state proceedings carefully and to prepare to counteract any effort to arm Marylanders against federal troops. Two days later, as Northern troops traveled through Maryland to defend the nation’s capital, Lincoln authorized the military to suspend the writ of habeas corpus along a transportation route deliberately chosen to avoid Baltimore and the secessionist mobs that had already attacked troops transiting through the city. General Cadwalader referred to this order in his explanation of why he would not appear with John Merryman before Chief Justice Taney.
The memorandum of May 17 responded to military arrests in Washington, D.C., and reflected Lincoln’s recurring discomfort with the suspension of habeas, even as he defended the need for limiting civil liberties to secure the Union.
[Documents Source: The Collected Works of Abraham Lincoln, Roy P. Basler, et al., eds., 9 vols. (New Brunswick, NJ: Rutgers University Press, 1953), 4: 344, 347, 372.]
Abraham Lincoln to Winfield Scott, April 25, 1861
I therefore conclude that it is only left to the commanding General to watch, and await their action, which, if it shall be to arm their people against the United States, he is to adopt the most prompt, and efficient means to counteract, even, if necessary, to the bombardment of their cities—and in the extremest necessity, the suspension of the writ of habeas corpus.
Abraham Lincoln to Winfield Scott, April 27, 1861
You are engaged in repressing an insurrection against the laws of the United States. If at any point on or in the vicinity of the military line, which is now used between the City of Philadelphia and the City of Washington, via Perryville, Annapolis City, and Annapolis Junction, you find resistance which renders it necessary to suspend the writ of Habeas Corpus for the public safety, you, personally or through the officer in command at the point where the resistance occurs, are authorized to suspend the writ.
Memorandum [May 17, 1861]
Unless the necessity for these arbitrary arrests is manifest, and urgent, I prefer they should cease.