In early 2004, Sahar Aziz, a law student at the University of Texas at Austin, organized a conference called "Islam and the Law: The Question of Sexism." The seminar attracted several hundred people. Unbeknownst to Aziz, who is Muslim, in the audience were two Army lawyers in civilian attire. They reported to military intelligence that three Middle Eastern men had asked them "suspicious" questions about their identity during a refreshment break. A few days later, two military intelligence agents materialized on campus, demanding to see a video-tape of the seminar along with a roster of attendees.
Aziz didn't respond and instead helped arrange a press conference. When the Wall Street Journal highlighted the episode in a story about domestic intelligence gathering by the military, the Army's Intelligence and Security Command acknowledged that the agents "exceeded their authority" and introduced "refresher training" on the limits of the military's jurisdiction.
As it turns out, though, it may be the public that needs a refresher course on the role of its military forces. In 2002, the Defense Department updated its Unified Command Plan, which made the already blurry lines between civilian and military even less legible. Since then, all over America, law enforcement and intelligence agencies have been making information about the public available to a Pentagon power center most people have never heard about: U.S. Northern Command, or NORTHCOM, located at Peterson Air Force Base in Colorado Springs. Hidden deep inside Cheyenne Mountain, more than 100 intelligence analysts sift through streams of data collected by federal agents and local law en- forcers-continually updating a virtual picture of what the command calls the North American "battlespace," which includes the United States, Canada, and Mexico, as well as 500 miles out to sea. If they find something amiss, they have resources to deploy in response that no law enforcement agency could dream of. They've got an army, a navy, an air force, the Marines, and the Coast Guard.
The creation of NORTHCOM, as part of the "unified plan" in the wake of 9/11, established the military's first domestic combatant command center. This precedent departs from a long-standing tradition of distinguishing between the responsibilities of the military and those of law enforcement. Since 1878, when Congress passed the Posse Comitatus Act in response to interference in elections by federal troops, an underlying assumption of U.S. democracy has been that soldiers should not act as police officers on American soil. While the Chinese army might send tanks to Tiananmen Square and the Liberian military might man checkpoints in the capital, the presence of National Guardsmen, carrying firearms and dressed in camouflage, patrolling American territory in the weeks after 9/11 was a striking anomaly.
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http://www.motherjones.com/news/outfront/2005/05/battlespace_america.html