Martial Law for Game-Changing Strategic Shocks?

One of the government's prime constitutional responsibilities is to insure domestic tranquility. Against this backdrop, New York Post financial columnist John Crudele is concerned that martial law might be invoked in the event of a further domestic economic meltdown or other forms of "strategic shock." The 52-page monograph he's referring to, which apparently was a lump of coal in his Christmas stocking, was released by the U.S. Army War College's Strategic Studies institute, and can be downloaded here. The report warns military decisionmakers (presumably USNORTHCOM) to prepare for the inevitability of future disruptive, unconventional shocks, i.e., the so-called Known Unknowns. In pertinent part, the author says that...

Widespread civil violence inside the United States would force the defense establishment to reorient priorities in extremis to defend basic domestic order and human security. Deliberate employment of weapons of mass destruction or other catastrophic capabilities, unforeseen economic collapse, loss of functioning political and legal order, purposeful domestic resistance or insurgency, pervasive public health emergencies, and catastrophic natural and human disasters are all paths to disruptive domestic shock...A whole host of long-standing defense conventions would be severely tested. Under these conditions and at their most violent extreme, civilian authorities, on advice of the defense establishment, would need to rapidly determine the parameters defining the legitimate use of military force inside the United States.

The military has increasing played a major role in disaster relief, but the kind of doomsday scenario outlined in the monograph raises a host of legal issues, under the Posse Comitatus Act and other laws.