If the product does not belong to the customer, it is illegal to damage it prior to its purchase. Tort law places the responsibility of an unowned item to the consumer, notes Slate. Removing the sticker can be considered negligent to the vehicle, where the buyer can be held responsible to pay for its repair.
Until the vehicle is purchased, the prospective buyer is held liable to any damage it incurs. However, once a vehicle is going to be purchased, the buyer has freedom to discuss the sticker's removal from the vehicle's window, notes the Globe and Mail. Some driver's make a point to ask the dealerships directly as they may feel the stickers are a distraction.