willow

We own a house in Normandy and on our last  visit (last week) we found that our box hedge (very old) was cut back and a tree within the hedge had been cut down by our neighbour!! I spoke with the chap and he said that the tree had fallen over into his garden so he had to cut it down. The hedge looks awful and we can now see into his garden and watch them in their gazebo! We used to tie our washing line to this tree and it was perfectly ok when we left in mid July. I have found one of the boundary blocks with the red dot on top at the front of our house on the right hand side as you look at it and know that there is one of these blocks up behind our shed which runs in more or less a straight line to the one at the front. Now the question is - how do I  find out if he has cut the tree and box back illegally. How are the boundaries determined in France??? can anyone help me - Willow