According to California state statutes on impaired driving, you can be convicted of California DUI even if you haven't had a single drink. Driving under the influence of drugs is just as illegal as drinking and driving. It doesn't matter if the drugs are legal or illegal. In fact, Section 23630 of the Vehicle Code states that even if a person is entitled to use a particular drug, it's still a crime to drive under the influence of a drug. If the police officer believes you are DUI from being under the influence of a drug other than alcohol, you will be required to provide either a blood test or a urine test.