There are regulations preventing the importation of live crayfish, but nothing that says you can't use native crayfish except for parts of the Pit River.
Importation of any live crayfish into California requires a permit issued by the Department. Live importation of exotic species of crayfish also requires authorization of the California Fish and Game Commission. ... Section 671 of Title 14, CCR, prohibits the importation or release alive in California of any species of crayfish of the family Cambaridae, except Procambarus clarkii and Orconectes virilis.” - Regulations governing take, sale or transport of crayfish for commercial purposes [Last viewed 22 January 2009]
Crayfish shall not be used for bait in the Pit River and all tributaries between Pit 3 Dam (Lake Britton) and the Fall River-Cassel Road Bridge at Fall River Mills, California (includes Hat Creek and Fall River and their tributaries).
So no buying live crayfish off the internet for bait, but I see no reason not to catch your own. Do you have a cite for someone saying you can't do it?