i believe the law reads you cannot damage the cambian layer of the tree, which is underneath the bark. trees like red maples and such damage very very easily...i wouldnt recommend climbing them. i usually only climb oaks or other thick barked trees. i also stay away from cherry and other such trees that have loose ragged bark that breaks off easy...not technically doing damage..but im sure they can say you did, and it gives away your spot. you cant tell when i climb oaks and such most of the time.