California Code, Health and Safety Code - HSC § 114075

(a) Except for refilling a consumer's drinking cup or container without contact between the pouring utensil and the lip-contact area of the drinking cup or container, food employees shall not use tableware, including single-use articles, soiled by the consumer, to provide second portions or refills.

(b) Except as specified in subdivision (d), self-service consumers shall not be allowed to use soiled tableware, including single-use articles, to obtain additional food from the display and serving equipment.

(c) Consumers shall be notified that clean tableware is to be used when they return to self-service areas such as salad bars and buffets.

(d) Drinking cups and containers may be reused by self-service consumers if refilling of a consumer's drinking cup is done without contact between the pouring utensil and the lip contact area of the cup or container.

(e) Personal take-out beverage containers, such as thermally insulated bottles, nonspill coffee cups, and promotional beverage glasses, may be refilled by employees or the consumer if refilling is a contamination-free process as specified in subdivision (a).