This is from the California CHP site:
http://www.chp.ca.gov/community/chil...seat_faqs.html
California's New Child Passenger Safety Law effective January 1, 2012
California Law will require children to ride in the back seat in a properly secured child passenger safety restraint until they are at least 8 years old or until they are at least 4 feet 9 inches in height.
Frequently Asked Questions
Why was the law revised?
Children are at greater risk when riding in the front seat. A child's injury risk is reduced by 33% when moved from the front seat to the back seat.
Are there exemptions?
Yes, there are a few. Your child may ride in the front seat if:
Your vehicle has no rear seats
Rear seats are side-facing jump seats.
Child safety restraints must never be placed on side-facing vehicle seats.
The child restraint system cannot be properly installed in the rear seat.
For example, your vehicle has lap belts only in the back seat, but there are lap and shoulder belts in the front seat. Your child is 5 and weighs 45 pounds and must ride in a booster seat. The booster seat must be used with a lap and shoulder belt; therefore your child may ride in the front seat.
Children under age 12 occupy all rear seats.
Medical reason (written by the pediatrician) requires that child not be restrained in the back seat. All children are safer in the back seat, ask another adult to ride with the child in the back.