I don’t know, that’s what I had heard somewhere.
The Constitution requires that Congress authorize any such use.
But then it also guarantees each state a republican form of government, something impossible unless the Founders envisioned possible use of the military against a particular state or its people.
It discusses suspending habeas corpus in time of invasion or insurrection. This implies that the people, or a group of them, might revolt and have to be suppressed.
While president, George Washington led a large federal army to suppress rebellion in western PA.