According to New York Times columnist Joe Nocera:
She is essentially claiming that the decision to publish — or even to allow — a Harry Potter encyclopedia is hers alone, since after all, the characters in her books came out of her head. They are her intellectual property. And in her view, no one else can use them without her permission.
“There have been a huge number of companion books that have been published,” Mr. Blair said. (Blair is Neil Blair, who works for the literary agency that represents Rowling.) “Ninety-nine percent have come to speak to us. In every case they have made changes to ensure compliance. They fall in line.” But, he added: “These guys refused to contact us. They refused to answer any questions. They refused to show us any details.”
Just imagine if that kind of grotesquely broad copyright claim is allowed to stand. Would reviewers be allowed to review books without getting prior approval of the author? Would scholarly treatments of major works be prohibited? Would students working on their dissertations be forced to pay royalties for quoting from published works? What would happen to encyclopedias?
Copyright holders have tried to impose rules on the rest of us — through threats and litigation — that were never intended to be part of copyright law...Have these efforts had — as we like to say in the news business — a chilling effect? You bet they have....No one is saying that anyone can simply steal the work of others. But the law absolutely allows anyone to create something new based on someone else’s art. This is something the Internet has made dramatically easier — which is part of the reason we’re all so much more aware of copyright than we used to be. But it has long been true for writers, filmmakers and other artists. That’s what “fair use” means.
What Ms. Rowling is saying, however, is that her control of Harry Potter is so all-encompassing that only she gets to decide the terms under which a companion book is allowable....This is really a power grab. RDR Books should not have to “fall into line” to publish the Lexicon. Ms. Rowling is claiming a right that, if granted, will hurt us all.
Will it be black magic? Rowling waves her wand and fair use rights disappear? Let's hope not.