TR,
I assume from your post that the President himself when he deems it necessary can not declare marshall law. I don't think that is correct. Did not Eisenhower send in troops from the 101st Airborne at Little Rock when Faubus declared that he would not let any black children into the high school. Did not the Clinton administration allow Delta Force to work with the Federal law enforcment agencies at Waco. Did not Teddy Roosevelt use regular army troops from the Embarcadara or perhaps the Presidio during the San Franscisco eathquake? Were there not U S Army reserve, not national guard, troops waiting in the wings during the Rodney King riots in Los Angeles to back up the U S Marshall and Federal Bureau of Prisons officers when they had to take back the streets of that city? These are just the ones from memory that I can recall.
FC