Originally Posted by
guerilla
Correct, posse comitatus act of 1878 prohibits the national guard, air force, marines, army and other military or paramilitary from operating with law enforcement or doing law enforcement duties themselves such as traffic control, checkpoints, arrests...etc
This was enacted right after the civil war and was an agreement to prevent future civil wars from presidents placing soldiers around the nation or amassing near state borders like the south, it was basically a peace agreement between the slave owners and non slave owners, and it still applies today. (well, not really because the government is spitting on it everyday by placing 500,000 soldiers in the streets of the entire nation, 500 thousand troops were deployed here in October of 2008 by the bush administration, and the policy continues to this day regardless of administration changes)
The other reason for it, is to prevent presidents or governors from using military to suppress dissent or peaceful citizens.
Julius Caesar did such a thing, which destroyed the republic of rome, and transformed it into an empire.
Remember, we are (were) a Republic, we are and have become a militaristic empire since the days of vietnam or even before some say.
This is also why we have a right to bear arms, to protect America from its government, or other foreign or domestic threats.