All 50 states and the District of Columbia have laws that specifically target drugged drivers. Almost one-third of states have adopted the per se standard that forbid any presence of a prohibited substance or drug in the driver's body while in control of the vehicle, without any other evidence of impairment. Others have established specific limits for the presence of intoxicating drugs, while still others follow a zero tolerance rule with regards to the presence of intoxicating drugs in a person's system.