While the production of porn has been decriminalized in California, prostitution is still illegal in CA, hence the reason adult contracts have so far not been recognized as valid contracts in CA. even though the adult industry has freedom to operate in CA.
I could be wrong here, but it's my understanding that in California, the State Supreme Court has recognized first amendment protections for the production of porn, including contracts with porn performers. It's only when the producer who is paying the performers also starts to interact with them sexually that it blurs into a potential (but untested) area of prostitution.
California is, as I understand it, the only state where the State Supreme Court has issued such a ruling regarding the production of porn.