Dogs have a very keen sense of smell... spray your lawn with something nasty. throw together a Jerry Baker mix of your urine (if you are a meat eater), cayenne pepper, garlic, tobacco juice (get little packets of chew and soak them), throw in some moth balls to soak for a bit and anything else stinky and rancid. Your neighbor is inconsiderate and rude to allow this and I hope you report him.

Put up a fence so the neighbor can't get in.

Confront him

There are very few animal problems that can't be solved with a paintball gun, a syringe, and some Nair. Use the syringe to suck out the paint, and refill the paintballs with Nair.

Beat him! lol

Put up a fence

dude, grow a sack and say something! don't just sit there and watch it happen (literally or metaphorically). c'mon man, if you don't speak up, they'll think its ok. people need to be treated like little kids sometimes... or like pets, and you should just shove their noses in it.

Lol piss-pipes and poop-chutes(:

call the police. they can give ur neighbor a fine.

Collect the poop in a bag, dump it in front of their doors, and leave thankyou notes.