You can't really. If they damage the land, or as in the case of the dogs, your livestock, you can take appropriate measures, but you can't stop people from being on your land as long as they haven't gained entry by force so to speak.Interesting. It's hard to imagine not having trespass laws. So how do you force someone to leave your property when they are unwelcome?
In many ways I approve of the lack of law with regard to trespass. I've always had difficulty with the idea that one can own a piece of a planet.
The lack of the law seems in general to work well. Lots of city people fence their land off, the locals tend not to unless they are trying to contain livestock.