Can my neighbor legally trim my tree without my knowledge or permission?

My neighbor or someone in his employ trimmed some limbs from a pear tree growing in my yard. These limbs extended over his property line. This tree is a non-fruiting tree. This neighbor knew the tree existed and that it had some overhang on his property. He has complained to me about it and I told him at the time that he knew the tree was there when he bought his house and if he wanted the limbs trimmed. He could do it at his own expense. These limbs impinge maybe five or six feet over his property line. I noticed today that the limbs had been trimmed. My wife, who is semi-ambulatory and is at home alone part of the day while I am at work, she told me that she heard all sorts of noise coming from next door. I don't really mind that the limbs are trimmed but I do mind that it was done without my knowledge and caused my wife some concern since she didn't know what was happening and can't get around quick enough to see what was going on.