[Possibly NSFW] Law buffs: What does the law say about professional dominatrices in California (Oakland, specifically)?

I have a debate going with someone regarding the legality of professional BDSM services in the SF Bay Area. They are saying it’s illegal and that from a police standpoint, ProDommes are no better than prostitutes. From all my research, because I was curious, it seems like it’s either legal or, in any case, not considered prostitution if the Dominant doesn’t engage in “sexual activity”. “Sexual activity” being generally defined as penis-vagina contact. Use of toys is not considered sex, legally, so far as I understand.

Now, my debate partner says that a lawyer has stated these professional domination activities are illegal, from start to finish, regardless of a session’s content. Of course, where the law is involved, I’m apt to trust a lawyer more than myself. However, I went back and started re-researching the law on this matter and I keep coming up with the same answer: Professional Dom/mes won’t be arrested around here unless there is “sex” involved.

Who’s correct? Is the truth somewhere in between (like, it’s illegal, but cops don’t care if no one’s getting laid)? Does anyone know?