Is declawing illegal in California?

No, declawing is legal in nearly all of California. It is banned in certain places however. The cities where declawing is banned in California are:

City	When Banned	Voting	Pop. of City
West Hollywood	2003	5/0	35,000
Santa Monica	27/10/2009	6/1	100,000
San Francisco	3/11/2009	9/2	810,000
Beverly Hills	5/11/2009	5/0	40,000
Los Angeles	6/11/2009	11/0	4 million
Berkeley	10/11/2009	9/0	125,000
Culver City	24/11/2009	5/0	39,000
Burbank	08/12/2009	4/1	100,000

The above table comes from a page on laws and cats.