During his two terms in office, George W. Bush stepped outside the boundaries of the Constitution and assembled an amazing toolbox of powers that greatly increased the authority of the Executive branch and the reach of the federal government.
Bush expanded presidential power to, among other things, allow government agents to secretly open the private mail of American citizens; authorize government agents to secretly, and illegally, listen in on the phone calls of American citizens and read our e-mails; assume control of the federal government following a "catastrophic event"; and declare martial law.
Thus, the groundwork was laid for an imperial presidency and a potentially totalitarian government--a state of affairs that has not ended with Barack Obama's ascension to the Oval Office, despite hopes to the contrary that President Obama would fully restore the balance between government and its citizens to a pre-Bush status quo.
The local police have, in many regards, already evolved into de facto extensions of the military. Dressed like Darth Vader look-alikes, the police have opted for the SWAT-team dress formally adopted by the federal agencies. Congressional legislation allows the U.S. military, by way of the Pentagon, to train civilian police. The Pentagon has also provided local police with military equipment such as M-16 rifles, bayonets, boats, vehicles, surveillance equipment, chemical suits and flak jackets, among other items. Thus, they are armed to the teeth.
We already have a federal police force comprised of Secret Service agents who are authorized to "carry firearms; make arrests without a warrant for any offense against the United States committed in their presence."