California Code, Code of Civil Procedure - CCP § 1974

No evidence is admissible to charge a person upon a representation as to the credit of a third person, unless such representation, or some memorandum thereof, be in writing, and either subscribed by or in the handwriting of the party to be charged. This section is a Statute of Frauds provision and is to be applied in a manner that is consistent with the manner in which subdivision 2 of Section 1624 of the Civil Code is applied.