Article II, Section 3:
He shall from time to time give to the Congress Information of the State of the Union, and recommend to their Consideration such Measures as he shall judge necessary and expedient; he may, on extraordinary Occasions, convene both Houses, or either of them, and in Case of Disagreement between them, with Respect to the Time of Adjournment, he may adjourn them to such Time as he shall think proper; he shall receive Ambassadors and other public Ministers; he shall take Care that the Laws be faithfully executed, and shall Commission all the Officers of the United States.
Whenever the President considers that unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States, make it impracticable to enforce the laws of the United States in any State or Territory by the ordinary course of judicial proceedings, he may call into Federal service such of the militia of any State, and use such of the armed forces, as he considers necessary to enforce those laws or to suppress the rebellion.
The President, by using the militia or the armed forces, or both . . . shall take such measures as he considers necessary to suppress, in a State, any insurrection, domestic violence, unlawful combination, or conspiracy, if it – (1) so hinders the execution of the laws of that State, and of the United States within the State, that any part or class of its people is deprived of a right, privilege, immunity, or protection named in the Constitution and secured by law . . . . 1
These quoted provisions of the United States Code consolidate a course of legislation that began at the time of the Whiskey Rebellion of 1792. 2 In Martin v. Mott, 3 which arose out of the War of 1812, the Court held that the authority to decide whether the exigency had arisen belonged exclusively to the President. 4 Even before that time, Jefferson had, in 1808, in the course of his efforts to enforce the Embargo Acts, issued a proclamation ordering
all officers having authority, civil or military, who shall be found in the vicinity of an unruly combination, to aid and assist
by all means in their power, by force of arms or otherwise the suppression of such combination. 5 Forty-six years later, Attorney General Cushing advised President Pierce that in enforcing the Fugitive Slave Act of 1850, marshals of the United States had authority when opposed by unlawful combinations to summon to their aid not only bystanders and citizens generally, but armed forces within their precincts, both state militia and United States officers, soldiers, sailors, and marines, 6 a doctrine that Pierce himself improved upon two years later by asserting, with reference to the civil war then raging in Kansas, that it lay within his obligation to take care that the laws be faithfully executed to place the forces of the United States in Kansas at the disposal of the marshal there, to be used as a portion of the posse comitatus. Lincoln’s call of April 15, 1861, for 75,000 volunteers was, on the other hand, a fresh invocation, though of course on a vastly magnified scale, of Jefferson’s conception of a posse comitatus subject to presidential call. 7 The provisions above extracted from the United States Code ratified this conception with regard to the state militias and the national forces.