Cal. Elec. Code § 9237

If a petition protesting the adoption of an ordinance, and circulated by a person who is a registered voter or who is qualified to be a registered voter of the city, is submitted to the elections official of the legislative body of the city in his or her office during normal office hours, as posted, within 30 days of the date the adopted ordinance is attested by the city clerk or secretary to the legislative body, and is signed by not less than 10 percent of the voters of the city according to the county elections official’s last official report of registration to the Secretary of State, or, in a city with 1,000 or less registered voters, is signed by not less than 25 percent of the voters or 100 voters of the city, whichever is the lesser, the effective date of the ordinance shall be suspended and the legislative body shall reconsider the ordinance.