Books with Licensing Contract on shrink wrap

Paul Deane writes “This year I have been recieving reference books with a license on shrink wrap. They have the same general message as most software does these days. Do not open unless you agree to the terms of the license…. The terms are not included. I would guess this is effort by publishers to extend rights to materials beyond copyright by claiming that material is licensed and anything they don’t like is a contract violation even though it is ok under copywrite. Can they get away with this?”