Speeders

I just got done watching an episode of the show "Speeders." For those unfamiliar with the show, it is one of those "follow along with the cops while they write traffic citations" shows, sort of like "Cops," but without the trailers.

The first person to be pulled over was pulled over by a Cop wearing the handle of "The Hammer." The sequence starts with the officer stating that he was looking for drunk drivers, and that he would use traffic violations as his probable cause to stop an unwary drunk. He soon spots a gentleman driving 60 in a 40 without his headlights on.

In the course of the traffic stop, the driver admits to one drink hours before, and smoking marijuana hours before. The Breathalyzer shows a blood alcohol of .06, which is below the limit of .08. "The Hammer" cites the driver for speeding, and then tells the driver that he is "not allowed to drive," and that he must find someone to come get him.

My question here is: Why? Since he is not legally drunk, on what authority does this officer tell the driver that he cannot drive? Since he is not legally intoxicated, he is not breaking the law by driving. If he is not breaking the law, then what power does this cop have to tell a person (whose only crimes were minor traffic offenses) that he cannot operate his vehicle?

Any police officers out there who would care to weigh in, please help me out here...