Cal. Health & Safety Code § 110285

In any case where the department has adopted a regulation prescribing a tolerance, including, but not limited to, a zero tolerance, for a poisonous or deleterious substance, food additive, pesticide chemical, or color additive in processed foods, the department may require manufacturers to guarantee that foods they market in the state comply with the tolerance. The department may require a guarantee periodically but in no case more often than once each calendar quarter.