Disaster relief? Call in the Marines.

As Washington picks through the lessons learned from hurricane Katrina, there is a growing conviction that the only organization with the skills, expertise, and resources needed to respond quickly to a catastrophe of such magnitude is the American military.

President Bush suggested a larger disaster relief role for the armed forces in his national address last week, and Congress has indicated it will take up the issue this autumn. Though the topic has emerged at other troubled times - most recently 9/11 - Congress has always avoided amending Posse Comitatus, the law that has kept active-duty soldiers out of civilian law-enforcement affairs since Reconstruction.

Anger over the scenes of chaos in New Orleans in the days after the hurricane, however, seems to have shifted the political landscape. It is an issue of profound importance both to the Pentagon and to the country at large, raising questions about the boundaries between the armed forces and American society - as well as the military's ability to press the war on terror abroad if it receives a new homeland mission.

"There's a strong historical precedent against doing this," says Michael O'Hanlon, a defense analyst at the Brookings Institution here. "But now we've got a real reason."

The difference is the scope of the destruction and the dire results of the delayed response, scholars say. During previous disasters, local responders were able to help many victims, while others were able to manage without power or shelter. Katrina, however, completely incapacitated local first-responders, and in the days before help arrived, New Orleans was beset by anarchy.

As officials look at what went wrong - and wonder what to do if a future disaster similarly eviscerates local responders - their attention has turned to the military. Clearly, the armed forces are best prepared to deploy quickly to devastated areas, bringing not only a clear command structure, but an array of resources ideally suited for difficult work - from mobile communication systems to troops trained for the most taxing conditions. In his Thursday address, Mr. Bush called the armed forces "the institution of our government most capable of massive logistical operations on a moment's notice."

As of yet, he has simply stated that "a challenge on this scale requires ... a broader role for the armed forces." Yet even before Bush's address, Sen. John Warner (R) of Virginia wrote a letter to Defense Secretary Donald Rumsfeld, saying that the Senate Armed Services Committee would be looking into "the entire legal framework governing a President's power to use the regular armed forces to restore public order in ... a large-scale, protracted emergency" - and asking Mr. Rumsfeld to do the same.

This framework rests on Posse Comitatus as well as the Insurrection Act, which together bar active-duty troops from engaging in domestic law-enforcement activities, unless there is essentially an open rebellion.

Reservations about granting the military too much power at home are older than the republic itself, harking back to days when British soldiers were foisted upon colonials for room and board. In the Constitution, the framers made specific provision to check military power by declaring that America's armed forces be directed by civilian authority - namely, the various secretaries of Defense.

Posse Comitatus goes even further, giving only National Guard units the authority to act as law enforcement, because they are under the control of governors. Active-duty troops are being used in the Gulf relief efforts but only for humanitarian efforts and logistical support. The move to amend Posse Comitatus would likely give them law-enforcement powers.

Yet the military has traditionally been among the strongest opponents, wary of any move that would take training time or money away from its fundamental mission: preparing for and waging war.

"If you create within the Department of Defense a primary mission to respond to these sorts of events, you're creating a huge additional burden," says retired Maj. Gen. Bruce Lawlor of the Joint Task Force - Civil Support. "The focus begins to shift, and that's not good."

Moreover, it would call upon soldiers to retask themselves, both mentally and physically, for a different mission. Still, some analysts suggest that rescue missions like the one in New Orleans actually dovetail well with the new face of war - the peacekeeping and nation-building going on in Iraq.

But General Lawlor disagrees. "There is an advantage to the warrior ethos," he says. "Working counterinsurgency is a lot different from bringing aid and relief to people who are in distress."

He suggests that the lesson of Katrina was a lack of leadership at all levels: Emergency-response planners had everything they needed, he says, but they did a poor job of organizing it.

How significantly the military will be impacted by any effort to further incorporate it into disaster response will depend on the shape of future proposals. But the first step would likely be the amending of Posse Comitatus, and civil libertarians, too, worry that any change - however small - could be rash and misguided.

After 9/11, "the government immediately leapt to the conclusion that there was a lack of power," so it passed the Patriot Act, says Timothy Edgar of the American Civil Liberties Union, suggesting that a revised Posse Comitatus could give the military a keyhole to greater power down the road. "Changing the law in a way that threatens civil liberties isn't the answer to a problem of management."