A judge in New York City ruled yesterday that the wholesale commercial republication of sections of the Harry Potter series of books does not constitute a "fair" use under the broad and generous US copyright doctrine. U.S. District Judge Robert P. Patterson decided the proposed Harry Potter Lexicon, for which no permission was given, would cause "irreparable injury" to the original copyright holder (J. K. Rowling).
The author and publisher of the proposed reference text had argued that their use of Rowling's material was protected by the doctrine of Fair Use. This argument failed to pass the court test. Rowling has stated that she intends to create her own Harry Potter reference book, which means of course that the Lexicon in question would use her own original material to compete commercially against her.
Some more details of the ruling at CNN.com, the BBC and The New York Times.
Thanks to bookninja for the tip.