It was a No Pooping sign.

Personally I like this idea. On another forum I go to, there is a guy with a home office who had a dogwalker in his neighborhood who would bring her dog by, leashed, same time every day, and let it poop on his lawn. He documented this with a timer and a web cam actually but then he set his sprinkler timer to go off aimed right at the sidewalk at the time they went by. It only took twice before they never came back that way.

You could get motion sensors on rainbirds- lots of folks around us use them to keep deer out of the gardens.