The natural defense would be to have non-copyrighted things on the network as well. By assisting with any search, both legal searches as well as illegal ones, w

The natural defense would be to have non-copyrighted things on the network as well. By assisting with any search, both legal searches as well as illegal ones, with no way to disambiguate (unless you had a copyright checker yourself when receiving the search request) the search is now laundered.