Where is he eating it from? If it's a litter tray could you get one of those covered ones, or if you see the pup do it spray him with a water pistol every time to put him off. Or if it's your cat could you pick the mess up before the pup gets it?
My labrador is partial to a bit (in fact i've never known a dog not to be), I don't have a litter tray anymore but she finds it in the Garden if I don't keep an eye on her - thankfully most of its under a conifer at the front of my house where she doesn't have unsupervised access.....