Well its illegal now in most areas to shoot and kill dogs. Though they usually don’t die from rock salt shot or bird shot. Still if someone was able to prove you shot their dog and only hurt it you are looking at a federal crime. That is unless its attacking your livestock. You might consider an electric net fence. I think the fencing is somewhere around $70 for 140 feet or so. Pepper spray might be another non lethal solution. Bear spray. There are even motion sensing pepper spray devices sold for home security. I wouldn’t worry too much about a neighbor complaining about his dog coming back to him whimpering, crying and sneezing. Other methods might include use of dogs yourself, donkey’s and geese.