What legal agreement?
A disclaimer is not a legal agreement unless it is signed by the person who it affects. To make that kind of thing clear, say you have an open abandoned well in your front yard. So you put up a sign, "Not responsible for anyone falling in the well". Do you think you would be protected because of the sign?
I've seen some military facilities with signs basically saying that you'll get shot if you survive escalating the electrified fences. I never heard of anyone suing them.
cheers, caveman
