The First Sale Doctrine is what legally allows libraries to share information. This doctrine is a “set of exemptions to U.S. copyright law that permit consumers to resell used books or DVDs and libraries to loan books without seeking permission from publishers.” It is now being rethought because so much information is published in digital form. And, so librarians and everyone else devoted to information sharing needs to strongly advocate for fair use of both print and digital information as we start to see court cases and legislation involving information sharing.

http://lj.libraryjournal.com/2013/12/copyright/digital-firsts/