If he is using only the easement as his dog walk path, you can argue that it is not being used as ingress/egress as agreed. If he uses it as agreed, he has every right to walk, with the dog, on the easement. If your dogs attach them while in that easement, you are liable as he has a legal right to be where he is without challenge.
just realize that if he is using the easement as a walk path and you object, all he has to do is check the mail or some other justification for walking down the easement.

