I searched the California Department of Fish and Game and found nothing prohibiting the keeping of the Peacock Bass. This may be due to the fact that this is a Tropical fish that would have little chance to establish itself in California Waters. That said, this has not stopped California form banning the Piranha when ALL documented evidence shows they could never establish in California water either (believe or not, the water gets too cold in the winter in CA).

I would recomend writing the CA Dept. of Fish and Game just to be sure.
Here is their web site:
http://www.dfg.ca.gov/