Neighbor Dog Keeps Pooping in My Yard

Yes, I'm pissed and normally I could ignore this but this is the third time this week. First time I thought okay I'll give it to them that it was cold and dog got mixed up, the second time I went out and the man was right there and even told me he had four dogs and not just the three that were out. I hadn't noticed the pile of dog crap at the bottom of my porch yet, I'd only went out to chase