Try here http://ag.ca.gov/firearms/travel.htm
Traveling with Firearms in California
California Penal Code section 12025 does not prevent a citizen of the United States over 18 years of age who is not within any of the classes excepted from firearm possession and who resides or is temporarily in California from transporting by motor vehicle any pistol, revolver, or other firearm capable of being concealed upon the person if the firearm is unloaded and in a locked container.
The term "locked container" means a secure container which is fully enclosed and locked by a padlock, key lock, combination lock, or similar locking device. This includes the trunk of a motor vehicle, but does not include the utility or glove compartment. For more information, refer to California Penal Code Section 12026.1.
OOps forgot to add make sure you have NO loaded magazines.