Posse Comitatus and police militarization
Why does a rural sheriff's department in Wisconsin need a Mine Resistant Ambush Protection Vehicle (MRAP) designed to protect soldiers in a war zone from land mines, improvised explosive devices and rocket-propelled grenades? Are shoplifters and methamphetamine addicts carrying military-grade equipment procured from terrorist organizations? For that matter, why does West Lafayette need a MRAP? Exactly how militant are those engineering students at Purdue? Do college parties get that much out of hand?
Congress passed the Posse Comitatus act in 1878 to strictly restrict the use of the military for domestic law enforcement. While giving armored military vehicles to police is not technically the use of the military for law enforcement, making law enforcement into a pseudo-military organization certainly breaks the spirit of the law and should be a real concern for Americans who value their civil liberties. This is an overreaction to our culture's paranoia about crime, despite the fact that violent crime has been falling for twenty years.
The problem with blurring the lines between military and police is that the two have very different missions. The police are to arrest criminals, yes, but also to protect and serve the community in various other ways. The military's job is to fight wars: They are to kill people and break things. Therefore, the category of people the military is designed to interact with - enemy soldiers - are entirely different from the civilian population that the police interact with.
This is why mixing military and police is dangerous. Police should not see the citizens they are supposed to protect and serve in the same way that the military sees foreign soldiers and/or terrorists. Militarizing the police creates a natural tendency to see citizens as the military sees enemy soldiers - and that is very dangerous for civil liberties. We need to only look at the disaster in Waco twenty-one years ago this Sunday for why this is a frightening thing.