CA Bus & Prof Code Section 22435.11

(a)

Any person who engages in the business of shopping cart or laundry cart retrieval shall retain records showing written authorization from the cart owner, or an agent thereof, to retrieve the cart or carts and to be in possession of the cart or carts retrieved.

(b)

A copy of the record showing written authorization shall be maintained in each vehicle used for shopping cart or laundry cart retrieval.