MY DEAR SIR: The Maryland legislature assembles to-morrow at Annapolis, and not improbably will take action to arm the people of that State against the United States. The question has been submitted to and considered by me whether it would not be justifiable, upon the ground of necessary defense, for you, as General in Chief of the United States Army, to arrest or disperse the members of that body. I think it would not be justifiable nor efficient for the desired object.
First. They have a clearly legal right to assemble, and we can not know in advance that their action will not be lawful and peaceful, and if we wait until they shall have acted their arrest or dispersion will not lessen the effect of their action.
Secondly. We can not permanently prevent their action. If we arrest them, we can not long hold them as prisoners, and when liberated they will immediately reassemble and take their action; and precisely the same if we simply disperse them--they will immediately reassemble in some other place.
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.
Your obedient servant,
Abraham Lincoln, Executive Order Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/203316