To put this bluntly, if you are currently living in California and looking to get a ferret you should rethink your decision. It is not legal to keep ferrets in the state of California.
This is believed to be due to a fear of the possible instability of the animal kingdom in that region. It is believed such occurrences of people letting their ferrets outside would lead to sudden extinction of many species of animal.
Although in most near locations that are not within California's borders it is legal to keep ferrets as long as they are fixed so this "issue" cannot come to play itself out.
There is though certain rumors of a secret society in which you can get help in finding ferrets and possessing one in California. This group ironically meets in a humane society. So how secret could they really expect people to believe it is? There is mention of this society on the websites stated at the bottom of the page.
Although if you really must have a ferret and do not actually care about the laws there are always breeders websites on the internet, but I cannot promise this method will work, being most animal breeders will not ship to locations that do not want the species within their borders. That not only puts you in danger of prosecution but the breeder also.
There are many ongoing attempts to make ferrets in California legal, you can join the effort in trying to change the ferret world on the websites stated on the bottom of the page.
And as unbelievable as this may sound there is a public website for an entire community of ferret owners and vets in California who come together in helping each other along the long road of ferret ownership in California.
No matter how discouraged you feel being limited to either hiding your ferret or not owning one at all. Just know you are not alone. And all these given societies take in people just as yourself with open helping arms to walk you through your troubles.
In the events which have passed and the constant attitude changes it is inevitable that the legalization of ferrets will either come to be in California or the actual possession of ferrets will just be overlooked due to the large numbers of activists and outraged families that would emerge from their silence.
Ferrets are no different from any other household pet, just because they require a little more work to keep healthy and comfortable, doesn't mean they don't deserve the same position in ones house.
California Domestic Ferret Association