Legal Question in Real Estate Law in California

I used the socratic method with myself to answer your own question. It goes like this:

Me: "How did the potential buyer's agent get into the house?"

Myself: "There is usually a lockbox on the door for access for agents when the owner is not home."

Me: "By agreeing to have a lockbox on the door, didn't the seller realize that people would look at the property when they were not there?"

Myself: "They should have. This person sounds like a troublemaker."

Well, crim inal cases are opened and prosecuted by district attorneys (DAs), often upon getting a report from the police or sheriff. In your instance, were the police summoned, and did they make a report? Based on my somewhat limited criminal-law experience (three years as a law clerk in the public defender's office while in law school) plus basic education in criminal law, I'm rather doubtful that what happened meets the definition of any crime, at least any that the local DA is likely to prosecute. I don't see anything alleging or pointing to a criminal intent. Was entry via a lock box? Unlocked door? Was any harm done, anything taken, by the agent or the clients? It would be hard for a DA to allege all the elements of any crime and obtain a conviction. Also, seems as though it would be hard to get any civil damages if the intruding agent or his clients did nothing further with the "personal information" they may have gained. I'd suggest you complain to the broker who employs the agent, and talk with someone at the DA's office if you feel that strongly, but that's about as far as this is likely to go. The DA's people will tell you they have their hands completely full prosecuting violent crime.