I once approached a car parked in the doctors car park, not only was he parked across two spaces, but he was throwing his drinks cans and other rubbish into the car park, I approached and asked him to please pick up his rubbish as the surgery staff were busy enough treating patients, he grudgingly got out of his car and picked up a can, but then he obviously had a think about it and got out of the car again and came and threatened to beat me up, to the point of pinning me against my car, and then when i was getting into the car, slamming the door against my leg, shortly after his wife came out and they departed, a passer by came and gave me his car registration, and when I went in to the surgery the staff asked me if I wanted a cup of tea and was i all right.
So what I am saying is if you do see someone who is just chucking their rubbish, its not always a good bet to approach them (he did take his rubbish away with him, though it probably ended up in the road around the next corner