Your car goes into a repair shop for diagnosis, weeks pass, and then the shop says you owe storage fees for a repair you say you never approved. That is the kind of dispute that can turn a bad repair experience into a full blown fight over who gets to keep the keys. The short answer is that a shop cannot simply invent rights it does not have, but whether it can hold the car often depends on state law, any signed paperwork, and whether the shop has a valid lien.