Cal. Elec. Code § 2138.5

Notwithstanding any other provision of law, an affiant’s driver’s license number, identification card number, and social security number, contained on an affidavit of registration or voter registration card, are confidential and shall not be disclosed by an individual or organization that distributes voter registration cards pursuant to subdivision (b) of Section 2158, or by any person entrusted with an affidavit of registration from an elector pursuant to paragraph (1) of subdivision (b) of Section 2158. However, this section shall not be construed to prohibit a person entrusted with an affidavit of registration from an elector pursuant to paragraph (1) of subdivision (b) of Section 2158 from returning that affidavit to the person or organization that distributed the voter registration card pursuant to subdivision (b) of Section 2158.