California Code, Elections Code - ELEC § 9035

An initiative measure may be proposed by presenting to the Secretary of State a petition that sets forth the text of the proposed statute or amendment to the Constitution and is certified to have been signed by registered voters equal in number to 5 percent in the case of a statute, and 8 percent in the case of an amendment to the Constitution, of the voters for all candidates for Governor at the last gubernatorial election preceding the issuance of the circulating title and summary for the initiative measure by the Attorney General.