California Code, Elections Code - ELEC § 17100

(a) All nomination documents and signatures in lieu of filing fee petitions filed in accordance with this code shall be held by the officer with whom they are filed during the term of office for which they are filed and for four years after the expiration of the term.

(b) Thereafter, the documents and petitions shall be destroyed as soon as practicable unless they either are in evidence in some action or proceeding then pending or unless the elections official has received a written request from the Attorney General, the Secretary of State, the Fair Political Practices Commission, a district attorney, a grand jury, or the governing body of a county, city and county, or district, including a school district, that the documents and petitions be preserved for use in a pending or ongoing investigation into election irregularities, the subject of which relates to the placement of a candidate's name on the ballot, or in a pending or ongoing investigation into a violation of the Political Reform Act of 1974 (Title 9 (commencing with Section 81000) of the Government Code).

(c) Public access to the documents described in subdivision (a) shall be limited to viewing the documents only. The public may not copy or distribute copies of the documents described in subdivision (a) that contain signatures of voters.