Wasn't this why the National Guard was created?

To avoid conflict with the Posse Comitatus Act?:

The U.S. military expects to have 20,000 uniformed troops inside the United States by 2011 trained to help state and local officials respond to a nuclear terrorist attack or other domestic catastrophe, according to Pentagon officials.

The long-planned shift in the Defense Department's role in homeland security was recently backed with funding and troop commitments after years of prodding by Congress and outside experts, defense analysts said.

There are critics of the change, in the military and among civil liberties groups and libertarians who express concern that the new homeland emphasis threatens to strain the military and possibly undermine the Posse Comitatus Act, a 130-year-old federal law restricting the military's role in domestic law enforcement.

But the Bush administration and some in Congress have pushed for a heightened homeland military role since the middle of this decade, saying the greatest domestic threat is terrorists exploiting the proliferation of weapons of mass destruction.

[snip]

Domestic emergency deployment may be "just the first example of a series of expansions in presidential and military authority," or even an increase in domestic surveillance, said Anna Christensen of the ACLU's National Security Project. And Cato Vice President Gene Healy warned of "a creeping militarization" of homeland security.

"There's a notion that whenever there's an important problem, that the thing to do is to call in the boys in green," Healy said, "and that's at odds with our long-standing tradition of being wary of the use of standing armies to keep the peace."

The National Guard:

Established under Title 10 and Title 32 of the U.S. Code, state National Guard serves as part of the first-line defense for the United States.[3] The state National Guard is divided up into units stationed in each of the 50 states and U.S. territories and operates under their respective state governor or territorial government [4]. The National Guard may be called up for active duty by the state governors or territorial commanding generals to help respond to domestic emergencies and disasters, such as those caused by hurricanes, floods, and earthquakes.[4]

With the consent of state governors, members or units of state National Guard may be appointed to be federally recognized armed force members in active or inactive service [5][6][7]. If so recognized, they become part of the National Guard of the United States [1]. The National Guard of the United States units or members may be called up for federal active duty in times of Congressionally sanctioned war or national emergency [4]. State National Guard may also be called up for federal service, with the consent of state governors, to repel invasion, suppress rebellion, or execute federal laws if the United States or any its states or territories are invaded or is in danger of invasion by a foreign nation, or if there is a rebellion or danger of a rebellion against the authority of the federal government, or if the President is unable with the regular armed forces to execute the laws of the United States [8]. Because both state National Guard and the National Guard of the United States relatively go hand-in-hand, they are both usually referred to as just National Guard.

Maybe I've answered my own question: (my bold)

The Posse Comitatus Act and the Insurrection Act substantially limit the powers of the federal government to use the military for law enforcement.

The Posse Comitatus Act is a United States federal law (18 U.S.C. § 1385) passed on June 16, 1878 after the end of Reconstruction. The Act prohibits most members of the federal uniformed services (the Army, Air Force, and State National Guard forces when such are called into federal service) from exercising nominally state law enforcement, police, or peace officer powers that maintain "law and order" on non-federal property (states and their counties and municipal divisions) in the former Confederate states.

The statute generally prohibits federal military personnel and units of the National Guard under federal authority from acting in a law enforcement capacity within the United States, except where expressly authorized by the Constitution or Congress. The Coast Guard is exempt from the Act.

Any militarization of our country is a dangerous thing and needs to be controlled carefully.

Will the ray be turned against citizens who protest the coup?

After years of testing, the Active Denial System -- the pain ray which drives off rioters with a microwave-like beam -- could finally have its day. The Army is buying five of the truck-mounted systems for $25 million. But the energy weapon may face new hurdles, before it's shipped off to the battlefield; a new report details how the supposedly non-lethal blaster could be turned into a flesh-frying killer.

Via Gandhisxmas of Pygalgia, Naomi Wolf reminds us why we should be concerned:

...the First Brigade of the Third Infantry Division, three to four thousand soldiers, has been deployed in the United States as of October 1. Their stated mission is the form of crowd control they practiced in Iraq, subduing "unruly individuals," and the management of a national emergency. I am in Seattle and heard from the brother of one of the soldiers that they are engaged in exercises now. Amy Goodman reported that an Army spokesperson confirmed that they will have access to lethal and non lethal crowd control technologies and tanks.

The article finishes with an interview with a retired Air Force colonel:

I interviewed Vietnam veteran, retired U.S. Air Force Colonel and patriot David Antoon for clarification:

"If the President directed the First Brigade to arrest Congress, what could stop him?"

"Nothing. Their only recourse is to cut off funding. The Congress would be at the mercy of military leaders to go to them and ask them not to obey illegal orders."

"But these orders are now legal?'"

"Correct."

"If the President directs the First Brigade to arrest a bunch of voters, what would stop him?"

"Nothing. It would end up in courts but the action would have been taken."

"If the President directs the First Brigade to kill civilians, what would stop him?"

"Nothing."

"What would prevent him from sending the First Brigade to arrest the editor of the Washington Post?"

"Nothing. He could do what he did in Iraq -- send a tank down a street in Washington and fire a shell into the Washington Post as they did into Al Jazeera, and claim they were firing at something else."

"What happens to members of the First Brigade who refuse to take up arms against U.S. citizens?"

"They'd probably be treated as deserters as in Iraq: arrested, detained and facing five years in prison. In Iraq a study by Ann Wright shows that deserters -- reservists who refused to go back to Iraq -- got longer sentences than war criminals."

"Does Congress have any military of their own?"

"No. Congress has no direct control of any military units. The Governors have the National Guard but they report to the President in an emergency that he declares."

"Who can arrest the President?"

"The Attorney General can arrest the President after he leaves or after impeachment."

[Note: Prosecutor Vincent Bugliosi has asserted it is possible for District Attorneys around the country to charge President Bush with murder if they represent districts where one or more military members who have been killed in Iraq formerly resided.]

"Given the danger do you advocate impeachment?"

"Yes. President Bush struck down Posse Comitatus -- which has prevented, with a penalty of two years in prison, U.S. leaders since after the Civil War from sending military forces into our streets -- with a 'signing statement.' He should be impeached immediately in a bipartisan process to prevent the use of military forces and mercenary forces against U.S. citizens"

"Should Americans call on senior leaders in the Military to break publicly with this action and call on their own men and women to disobey these orders?"

"Every senior military officer's loyalty should ultimately be to the Constitution. Every officer should publicly break with any illegal order, even from the President."

"But if these are now legal. If they say, 'Don't obey the Commander in Chief,' what happens to the military?"

"Perhaps they would be arrested and prosecuted as those who refuse to participate in the current illegal war. That's what would be considered a coup."

"But it's a coup already."

"Yes."

Soldiers from Iraq duty being brought home

And being toughed up to deal with protesters:

The 3rd Infantry Division’s 1st Brigade Combat Team has spent 35 of the last 60 months in Iraq patrolling in full battle rattle, helping restore essential services and escorting supply convoys.

Now they’re training for the same mission — with a twist — at home.

Beginning Oct. 1 for 12 months, the 1st BCT will be under the day-to-day control of U.S. Army North, the Army service component of Northern Command, as an on-call federal response force for natural or manmade emergencies and disasters, including terrorist attacks.

And: (my bold)

The colonel’s remark suggests that, in preparation for their“homefront” duties, rank-and-file troops are also being routinely Tasered. The brutalizing effect and intent of such a macabre training exercise is to inure troops against sympathy for the pain and suffering they may be called upon to inflict on the civilian population using these same “non-lethal” weapons.

According to military officials quoted by the Army Times, the deployment of regular Army troops in the US begun with the First Brigade Combat Team is to become permanent, with different units rotated into the assignment on an annual basis.

In an online interview with reporters earlier this month, NorthCom officers were asked about the implications of the new deployment for the Posse Comitatus Act, the 230-year-old legal statute that bars the use of US military forces for law enforcement purposes within the US itself.

Col. Lou Volger, NorthCom’s chief of future operations, tried to downplay any enforcement role, but added, “We will integrate with law enforcement to understand the situation and make sure we’re aware of any threats.”

Volger acknowledged the obvious, that the Brigade Combat Team is a military force, while attempting to dismiss the likelihood that it would play any military role. It “has forces for security,” he said, “but that’s really—they call them security forces, but that’s really just to establish our own footprint and make sure that we can operate and run our own bases.”

Lt. Col. James Shores, another NorthCom officer, chimed in, “Let’s say even if there was a scenario that developed into a branch of a civil disturbance—even at that point it would take a presidential directive to even get it close to anything that you’re suggesting.”

Update 9/27: Steve Bates of The Yellow Doggerel Democrat found the possible original link.

Making martial law easier

Slipped quietly into the defense budget bill, a provision put in:

at the Bush administration’s behest that makes it easier for a president to override local control of law enforcement and declare martial law.

The provision, signed into law in October, weakens two obscure but important bulwarks of liberty. One is the doctrine that bars military forces, including a federalized National Guard, from engaging in law enforcement. Called posse comitatus, it was enshrined in law after the Civil War to preserve the line between civil government and the military. The other is the Insurrection Act of 1807, which provides the major exemptions to posse comitatus. It essentially limits a president’s use of the military in law enforcement to putting down lawlessness, insurrection and rebellion, where a state is violating federal law or depriving people of constitutional rights.

The newly enacted provisions upset this careful balance. They shift the focus from making sure that federal laws are enforced to restoring public order. Beyond cases of actual insurrection, the president may now use military troops as a domestic police force in response to a natural disaster, a disease outbreak, terrorist attack or to any “other condition.”

Changes of this magnitude should be made only after a thorough public airing. But these new presidential powers were slipped into the law without hearings or public debate. The president made no mention of the changes when he signed the measure, and neither the White House nor Congress consulted in advance with the nation’s governors.

There is a bipartisan bill, introduced by Senators Patrick Leahy, Democrat of Vermont, and Christopher Bond, Republican of Missouri, and backed unanimously by the nation’s governors, that would repeal the stealthy revisions. Congress should pass it. If changes of this kind are proposed in the future, they must get a full and open debate.

Via Echidne