California has a three-tiered court system.
Image from: http://www.courts.ca.gov/2113.htm.
Cases, which are written opinions by a judge, are published for the California Supreme Court and the California Court of Appeals. Note: Trial (superior) court cases are generally not published and must be requested directly from the court.
For more information, see the websites below.
If you want to know where California case law is published, check out this map. For best results, view in the full-screen version.