The California Penal Code has this section:

12031. (a) (1) A person is guilty of carrying a loaded firearm when he or she carries a loaded firearm on his or her person or in a vehicle while in any public place or on any public street in an incorporated city or in any public place or on any public street in a prohibited area of unincorporated territory.

That basically criminalizes openly carrying a loaded firearm any place that isn't extremely rural and further in the code there is an exception for hunting. What's most interesting is seeing why the law is there. For that I turn to this excellent set of photos from the LA Times:

Yep. That law is racially neutral... The Panthers did the same thing in Olympia Washington shortly after. They didn't get inside the building but the police response was far less reactionary. If I remember correctly, Washington abandoned their proposed law along the same lines.

I need to find a copy of the film, but there is a very funny moment where Willie Brown tries to remain neutral when the Panthers enter the chambers.

Update: This scholarly work has some more of the historical background.

It takes a lot to make my better half this angry.

She's mad because Canada has become the laughing stock of freedom.