I'm not certain, but I think they have already done so.
Yes, Davis signed the "Reproductive Privacy Act" in 2002. (SB 1301, Kuehl; Assembly votes, Senate votes)
If Roe vs. Wade were ever overturned, allowing states to determine their own abortion policies, abortion would have become prohibited in CA due to preexisting laws. So, the Democrats authored the new law to guarantee the "right" to have an abortion in CA even if anything changed on the federal level.
Not true. In 1967 Governor Ronald Reagan as one of his first acts as governor signed a bill "liberalizing" abortion laws in California. That law however was nowhere nearly as permissive as Roe v Wade.
The fact that the California Assembly and Senate passed a law signed by Governor Gray Davis codifying the level of permissiveness in California that existed under Roe v Wade demonstrates that the real goal of polititicians like Barbara Boxer is not to defend the right of California to decide its own abortion laws but to force that level of permissivness of abortion on all the states. I might add that if it were up to politicans like Barbara Boxer, the state governments would effectively be abolished and leftist policies they espouse would also be forced on the whole country.