From Posse Comitatus and Nuclear Terrorism in PARAMETERS: US Army War College Quarterly:
Although Posse Comitatus as a matter of law may be rapidly weakening, the principles embodied in the act serve an important and essential role within the American constitutional system. Even during a domestic nuclear terrorist incident, further erosions of Posse Comitatus are neither necessary nor advisable. Advocates of an expanded military role correctly note that many of the homeland defense missions they envision for the Army have a firm constitutional basis, including the Preamble’s call to “insure domestic tranquility” and “provide for the common defense.”[14] However, these analysts sometimes fail to acknowledge the Founding Fathers’ significant concerns regarding the effects of a large standing army on a democratic government. As evidenced by the Second and Third Amendments to the Constitution, the Framers clearly preferred a small standing army to be augmented by a “well-regulated militia” in times of crisis over a larger, permanent military force. George Washington, the first American Commander-in-Chief, endorsed a standing army only under limited conditions: “`Altho’ a large standing army in time of peace hath ever been considered dangerous to the liberties of a country, yet a few troops, under certain circumstances, are not only safe, but indispensably necessary.”[15] The Anti-Federalists went further, calling standing armies “that bane to freedom, and support of tyrants, and their pampered minions; by which almost all the nations of Europe and Asia, have been enslaved.”[16]
Despite the Founding Fathers’ preference for them, reliance upon slow-forming militias for national defense is obviously no longer possible from a strategic standpoint in the modern world. This fact, however, makes Posse Comitatus even more important, rather than less. The existence of a large standing army in a democratic nation requires significant restrictions to be placed upon the military’s domestic role for the sake of both the government and the military. As Air Force Colonel Charles Dunlap has remarked, “There are relatively few modern examples where systematic use of the military to meet internal security threats has been good for democracy or, for that matter, the military itself.”[17] The absence of restrictions on the military runs the risk of jeopardizing democratic institutions and of dragging the military away from its principal mission of defending the nation and into domestic politics. Thus, Posse Comitatus and the principles it embodies are more than “merely legal bars that could be corrected by additional legislation.”[18] There is nothing about Posse Comitatus that needs to be “corrected” except, perhaps, to strengthen it.
Ironically, probably the greatest proponent of continuing such restrictions on the US military is the military itself. DOD regularly resists further erosion of Posse Comitatus even as the Congress and, to a lesser extent, Presidents have called upon DOD’s impressive capabilities to fight everything from the war on drugs to the weather. No doubt DOD’s reluctance is based as much on a desire to husband resources as it is on a desire to honor certain principles, but the military is definitely the most consistent opponent of further military involvement in law enforcement affairs. In any event, as noted by Ms. Kayyem, “Neither concern about the public response to such an increased role, nor the Department of Defense’s historical reluctance, however, stand as a legal bar to the use of the military.”[19]