chopping his tree apart(without asking) is likely to piss him off a bit. However, you being a nice, civil human being and simply asking him if he minds you trimming, might cause a bit less trouble and at least will show some common courtesy.
Then again, if you are already on such bad terms that this guy doesn’t even want you on his property, well than it sounds like you are probably not very civil. In that case, might as well just cut down the tree so it falls on his house.