Legal Question in Civil Litigation in California

No. They have a right to get together and talk. If they tell lies in court you can ask the judge to impose sanctions on them.

You cannot sue for conspiracy. Conspiracy is not a civil cause of action. It is only a legal theory for making one person legally liable for the acts or omissions of another. It is similar to agency, where you can sue the principal for the actions of their agent. Likewise you can sue a conspirator for the conduct of their co-conspirators in certain circumstances. Fraud is the most common situation where conspiracy might be asserted. A and B conspire to defraud you, but only B makes the false representation to you. If it is a true conspiracy you can sue A as well as B in that case. The bottom line is that until there is a base for suing one conspirator, there is no grounds to sue any other conspirator. They are free to conspire to mess with you as long as the methods they use to mess with you are not illegal.

Mr. McCormick hits the nail right on the head. Conspiracy is not a theory of recovery, it is a form of vicarious liability. You would have to have an underlying cause of action, and then plead conspiracy to extend liability to the people participating in the conspiracy. Conspiracy alone is insufficient, it must be conspiracy to do something that the law recognizes as a legal wrong, and extends a remedy.