Given your scenario, a slap on the wrist. The max you can get for a ounce of marijuana in california not as a patient is a 100 dollar fine and is a misdemeanor. Assuming you have nothing on you, they can ticket you for being intoxicated in public if the cops are dicks. If the driver is under the influence then he could technically get a DUI. If you did have more than an ounce, and it was your first drug offense then you have to attend some classes. Only thing you should fear is loosing your sac.