Wrong Parking

I found a bunch of these stickers stuck on cars that were parked illegally. Anyone seen these before? The car I took a picture of had 3 of these stickers, one on the rear window, one on the front window and one on the side window. I don't think a cop stuck them because there were no tickets. I think someone who seems to have had enough of all the terrible parking decided to go around sticking these on cars. Pretty cool.