Insurrection Act of 1807

The subject law authorizes the President to send troops to deal with civil disorder without authorization by the subject State.

However, the Constitution, Article IV, Section 4, states:

"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."

So does the President need the approval of the Governor?

What is the constitutional basis of the Insurrection Act?