While I agree with Golnar, legally speaking, personally, I would just put up a fence and be done with it. I might consider also doing the reporting Golnar recommends because it wounds like the dogs would keep breaking through and this person's finances may be limited. There are also things you can use, even where there is no fence, such as a motion-activated sprinkler head that shoots water. I actually used that as a a "bonus" answer on a Property final regarding "creative" ways to deal with the prof''s neighbor, whose dog keeps coming on her property doing damage, and the prof loves animals so...what to do besides go all legal on him and the animal gets caught up. And law students need to learn how things work in the real world. Around here, it is very hilly and fences aren't necessarily useful, look lousy, it is expensive, etc.