Billions of federal dollars have been spent since September 11 on purchasing modern and often military-grade equipment for state and local police. But there is little that limits the use of that hardware to counter-terrorism purposes, and oversight of the spending is difficult, according to federal sources and documents reviewed by the Guardian.

In the wake of the Ferguson protests, much attention has gone to the Department of Defense's program to supply surplus military equipment to police. But that program is eclipsed in size and scope by grant money from the Department of Homeland Security (DHS), which enables purchases of similar "tactical" equipment.

Under existing federal requirements, police departments and state law enforcement agencies do not need to spend much of that money on preventing terrorism or preparing for disaster relief.