California does not have a "stop and ID" law, which means that are are not required to supply any ID to any law enforcement officer unless you need it to perform an activity (driving, hunting, etc.) or are under investigation of a crime.
Also, if you are under investigation of a crime, you don't have to "show" ID - simply stating your name, address, and date of birth is enough. If you aren't required to have a license to do what you were doing, you aren't required to show any ID.
So if you are ever approached by the police in CA and they ask for ID (and you aren't doing anything that requires a license), politely refuse if you want, even if you are a passenger in a car.
My home state (PA) does not have one either. I was requested by a local officer to give ID and I refused. He tried to threaten, but in the end I walked away without hardly saying a word (you are never, ever required to speak to the police).