they don’t, just like they don’t need a law saying you can’t text and drive because it’s distracted driving which is already illegal. but now you can question it less when they go to take your phone. it gets rid of the grey area and instead of the cop saying well the phone could of led to the accident so i can take it to look because a law says i can investigate anything that could cause an accident they now can say the law says u got in an accident so i can take your phone.