U.S. Const, Art 4, Sec 4: "The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence."
The Militia Act of 1795: "That whenever the United States shall be invaded, or be in imminent danger of invasion, from any foreign nation or Indian tribe, it shall be lawful for the President of the United States to call forth such number of the militia of the state or states, most convenient to the place of danger, or scene of action, as he may judge necessary to repel such invasion, and to issue his orders, for that purpose, to such officer or officers of the militia as he shall think proper. And in case of an insurrection in any state, against the government thereof, it shall be lawful for the President of the United States, on application of the legislature of such state, or of the Executive, (when the legislature cannot be convened,) to call forth such number of the militia of any other state or states, as may be applied for, as he may judge sufficient to suppress such insurrection."
"And be it further enacted, That whenever the laws of the United States shall be opposed or the execution thereof obstructed, in any state, by combinations too powerful to be suppressed by the ordinary course of judicial proceedings, or by the powers vested in the marshals by this act, the same being notified to the President of the United States, by an associate justice or the district judge, it shall be lawful for the President of the United States to call forth the militia of such state to suppress such combinations, and to cause the laws to be duly executed. And if the militia of a state, where such combinations may happen, shall refuse, or be insufficient to suppress the same, it shall be lawful for the President, if the legislature of the United States be not in session, to call forth and employ such numbers of the militia of any other state or states most convenient thereto, as may be necessary, and the use of militia, so to be called forth, may be continued, if necessary, until the expiration of thirty days after the commencement of the ensuing session."
Sorry. Wrong again. The President had an obligation to respond to the insurrection. Of course, you know that already.