In Michigan, you have the right to shoot and kill any predator, including dogs, that are attacking your livestock. A calmer solution would be to call animal control. Sometimes if animal control comes out and talks to the people that will get them to shape up. I don't know if animal control will do that in your area. You can always warn them that if the dog invades your property and attacks the chickens you may have to shoot it if you can in your area. I would do it in writing.