Hah! I love it. A city in Spain is getting revenge on dog poop law scoffers by delivering their dog's poop back to them at home. In Brunete, Spain, the mayor found that the most consistent complaint he received was about the presence of errant dog-poop so he set about to reduce this problem. His earlier program was less successful, more on that later, but this one works. All dog owners seem to be carrying plastic bags now, a rare sight in Spain and dog poop complaints have been reduced by 70%.
This article goes into more detail. The big question I had while reading it was: How do they know whose poop it is? Undercover volunteers, after witnessing a crime, will meet the owner and admire the dog, asking its name and breed. From there, a quick look at town records reveals the address. The poop is packaged in a white box and delivered to the door titled: Lost and Found. When the owner signs for the package, they get a lovely surprise.
Oh, and the previous failed project. A remote controlled plastic poop that would bump into people's feet to raise awareness. Both programs are shown in the video below: