I don’t see it as stretching regarding Neil’s suggestion but there may also be a local ordinance that may address hand billing by placing it on a car more directly.
Upon rereading the original post, I see that op is checking on legality due to their desire to use the method to advertise.
With that perspective in mind:
It appears there are laws that could be applied where you could be prosecuted. There are possibly more laws/ordinances that have not been discovered prohibiting the action. Whether you would be prosecuted would be up to the local police and/or prosecutor.
I can tell you that if I owned a business that somebody did this to my customers, I would offer a token reward to anybody that turned the flyers in to me. Then I would become hell’s hound and search out the culprit and stuff the flyers where it would be noticed the most by the distributor and cause them the most grief.
I am also certain some quantity of the flyers would end up on the ground at my business and I would have to pay an employee to pick them up. As a business owner I would use all the influence I could muster to seek the perpetrator be prosecuted and subjected to the heaviest penalty possible.
I loathe people that put crap on my windshield.
