The historic importance of the Posse Comitatus prohibition was also well-analyzed here.
As the recent militarization of St. Paul during the GOP Convention made abundantly clear, our actual police forces are already quite militarized. Still, what possible rationale is there for permanently deploying the U.S. Army inside the United States — under the command of the President — for any purpose, let alone things such as “crowd control,” other traditional law enforcement functions, and a seemingly unlimited array of other uses at the President’s sole discretion? And where are all of the stalwart right-wing “small government conservatives” who spent the 1990s so vocally opposing every aspect of the growing federal police force? And would it be possible to get some explanation from the Government about what the rationale is for this unprecedented domestic military deployment (at least unprecedented since the Civil War), and why it is being undertaken now?
UPDATE: As this commenter notes, the 2008 National Defense Authorization Act somewhat limited the scope of the powers granted by the 2007 Act detailed above (mostly to address constitutional concerns by limiting the President’s powers to deploy the military to suppress disorder that threatens constitutional rights), but President Bush, when signing that 2008 Act into law, issued a signing statement which, though vague, seems to declare that he does not recognize those new limitations.
UPDATE II: There’s no need to start manufacturing all sorts of scare scenarios about Bush canceling elections or the imminent declaration of martial law or anything of that sort. None of that is going to happen with a single brigade and it’s unlikely in the extreme that they’d be announcing these deployments if they had activated any such plans. The point is that the deployment is a very dangerous precedent, quite possibly illegal, and a radical abandonment of an important democratic safeguard. As always with first steps of this sort, the danger lies in how the power can be abused in the future.
— Glenn Greenwald