California Code, Civil Code - CIV § 1939.13

(a) A rental company shall not require the purchase of a damage waiver, optional insurance, or another optional good or service.

(b) A rental company shall not engage in any unfair, deceptive, or coercive conduct to induce a renter to purchase the damage waiver, optional insurance, or another optional good or service, including conduct such as, but not limited to, refusing to honor the renter's reservation, limiting the availability of vehicles, requiring a deposit, or debiting or blocking the renter's credit card account for a sum equivalent to a deposit if the renter declines to purchase the damage waiver, optional insurance, or another optional good or service.