@Mame,
In Private Parking lots, ie malls, stores blah, blah, blah...
Stores, businesses can deem who or what parks wherever.(except emergency lanes - fire lanes, and handicapped parking) ie. No-parking, staff parking, no-over night parking, restricted parking, mother/tots parking, yadda yadda. As long as signs are well posted (visible) and with the name/number of towing company that patrols the lot, ie ABC towing, they can enforce their own artificial rules. So, if walmart decides that you are parking illegally, under the Mom and Tot courtesy sign, they can have the towing company tow your car, and you will be fined, much like a trespassing ticket. In other words, if you the customer decide to thumb your nose at Walmarts parking lot rules and park in a courtesy parking spot, they can and will tow your car and fine you. This is well within their right, the own the lot and can do as they see fit.
Most places won't tow your vehicle as it is bad for business, but they DO have the right.