1st amendment is dead in California?
I’m not sure the first amendment issue is the best argument. The Supreme Court had recognized limitations on the first amendment not being absolute. I would be concerned that the argument maybe that misinformation would be akin to the proverbial yelling fire in a crowded theater.
While this law is clearly immoral on its face and government overreach, I would tend to think the better argument is that there is already a pathway for relief in a malpractice suite. If a physician commits the act of malpractice which would clearly include misinformation, the remedy would be a civil lawsuit. No need for this law which would be capricious and whimsically enforced.
I think this is the dagger argument in the heart of a court challenge to this law.