There’s no higher legal standard in a DUI case because the individual hold a CDL. They’re treated neither more lightly nor more harshly because of the CDL itself. However, if the person is found driving under the influence while driving a tractor trailer or some other large truck, in addition to the likelihood that they’ll lose their CDL on conviction, the court may treat the driver more harshly by virtue of the fact that more damage can be done in a larger vehicle than in a smaller one and the risk of injury or death is far greater.