Is towing a car without keys or consent lawful?

That would usually be called "grand theft, auto". If the bank gives a repo order, the bank is giving consent because they assert their ownership...they do hold the title. If a mechanic tows your car to another location to complete repair, that would depend on the contract. If you abandon your vehicle and it gets towed to impound because it was blocking traffic you have no recourse but to pay the impound fee. If you buy property with an abandoned vehicle, you can claim that vehicle under various statutes. You get into some scales of grey when you get into arguments of implied consent. If your garage is on fire and your neighbor drags your car out before it burns to the ground, you probably wouldn't want to charge him with theft.