I too would like to know how this is actually enforced. The stretch of grass behind my apartment building is constantly covered in cr*p, so much so that getting in and out of the car in the dark is a guessing game. My dog and I are out there several times a day, and the few people I've seen leaving "presents" have gotten an earful from me (or, occasionally, the Husband) because it's gross, illegal, and rude. If I can pick up Dane poop, you can pick up terrier poop, you know?
But yes, I'd call someone to issue a fine if that's what it took.
-"Grey. You said green men. A Reticulan's skin tone is actually grey. They're notorious for their extraction of terrestrial human livers, due to iron depletion in the Reticulan galaxy."
-"You can't be serious."
-"Do you have any idea what liver and onions go for on Reticula?"