In the State of California it is a defense to the possession of marijuana to have a valid doctor's recommendation for the use of marijuana for medical purposes. The Compassionate Use Act allows physicians to recommend the use of marijuana for certain specified medical conditions including "chronic pain". For those in possession of a vailid physician's recommendation, possession of up to eight ounces of dried marijuana is legal.

Prosecutors in Los Angeles and Orange County Courts often question the validity of doctor's recommendations and refuse to dismiss charges unless the defendant performs some penalties to earn a dismissal. This approach is not justified and Prosecutors and Judges sometimes need to be educated about the law and that they should not second guess the opinion of a doctor. In fact, in addition to dismissing possession charges, the court should also, upon motion, return the marijuana to the defendant. It is afterall, the patients medicine.

However, the above does not provide a defense to DUI charges in California. It is still possible to be prosecuted for DUI based on marijuana, despite the existence of a valid prescription. The issue then becomes whether the defendant was impaired to drive. There is little medical evidence to support a DUI prosecution based on marijuana alone and many prosecutors will agree to dismiss this charge as well.