[svandamme]

i'de give the neighbours a written notice that you told them not to touch your trees, and make em sign a duplicate of that notice, as proof that they read it...
that way you have proof that you told them not to , instead of them saying that you said it was ok verbally...

no point sticking any laws to any tree , if you're not there, they can remove it and deny it

camera's would not prove that you didn't agree to removing the trees at all