Legal Question in Civil Litigation in California

You can't. No case has to be filed in small claims if the plaintiff prefers a regular court. Choosing small claims involves giving up some rights, like the right to hire a lawyer and to conduct discovery, in exchange for advantages of cost and time, so it can't be forced on an unwilling plaintiff. (The defendant doesn't give up the same rights since he isn't there by choice.)

The plaintiff in your case is probably seeking attorney fees. You can't make it forfeit that right by moving the case to small claims against its will.

I need to correct part of my prior answer. Neither party in small claims court can have a lawyer or conduct discovery. But the defendant can appeal if he loses, while the plaintiff cannot.

I agree with Mr. Hoffman's response, both of them. You can't compel the plaintiff to refile or file any motions to have the case transferred to small claims.