The California bag ban applies to liquor stores, convenience stores, and stores with pharmacies (although the pharmacy itself can supply bags for meds.) it also applies to stores that sell certain canned goods, dry goods, and perishables. The last time I stocked up on cat food, the pet store manager thanked me for bringing my own bags. He was weary of dealing with SS customers who tell him he is lying and demand bags.
I do admit, however, that I really miss having a free supply of cat box bags.