Huummm. It will be interesting to see how this works out. I think he might have some problems if these guyswere just in his backyard. I'd say he'd be fine if they were trying to break into his house.
Honestly, I think someone has the right to defend all of his property. Unfortunately, that's not the way everyone sees it.
I will say that when I was working for the police department, we had a lady that shot a drunk guy trying to get into her back window. Come to find out, it was her neighbor that had gone out,gotten drunk,didn't have his house keys, and thought he was breaking into his own house. Police got there, made sure this is what happened, and she was fine. Police report said it was self-defense. I doubt it would have been the same if the guy was out in the backyard.