Just for the record, here's a summary of the CA child restraint laws.
http://www.carseat.org/Legal/99_Enf.pdf
While technically legal if the rear seat is removed, I know someone who got a ticket for having a child seat in the front anyway. He was cited for deliberately removing safety equipment (the rear seat) and having the child seat in the front. It probably didn't help that he was being a dick and told the cop that he removed the seat for that purpose. He also lost the case in court with the female judge calling him a danger to his child.