What about Seat Belt law?
CA Vehicle Code Section 27315 (4):
‘The operator of a taxicab shall not operate the taxicab unless any passengers eight years of age or over in the front seat, are properly restrained by a safety belt.’
Passengers who are at least 16 years old can be cited for failing to comply with the Seat Belt laws. Drivers are responsible for their own conduct along with their passenger's behavior, and can be cited for any seat-belt violation that occurs within their vehicle.
What about Child seat law?
The new California Booster Seat Law prohibits parents, guardians, or drivers from transporting on a highway in a motor vehicle any child under 8 years old without securing that child in a child restraint meeting federal motor vehicle safety standards. The new child safety seat law, which went into effect in January 2012, imposes stiff fines and penalties for violations, including the possibility of child endangerment charges.