Police Militarization: When Security Clashes with Liberty

Police forces everywhere are looking less like the patrolmen of the past and more like a modern military unit.  Weaponry has increased in scale and technical ability, providing greater protection for officers.  But has this come with equivalent protections for society or greater threats?  How should we feel when the law of the land is enforced through bomb wielding robots, tanks, and surveillance systems imported straight from warzones?