A group of crusading intellectual property lawyers at Stanford Law School say they will help defend a small publishing house being sued by author J.K. Rowling over its plan to print an unauthorized companion guide to her Harry Potter series.

The Fair Use Project at Stanford's Center for Internet and Society announced Tuesday that it had signed on to aid the defense of Michigan-based RDR Books, which had planned to release "The Harry Potter Lexicon" this fall.

The book's publication has been blocked by the lawsuit. Rowling and Warner Bros., which produces the Harry Potter movies and holds the copyright on the seven novels, have argued that the lexicon borrows too heavily from the books and amounts to copyright and trademark infringement.

Fair Use Project Executive Director Anthony Falzone said the lexicon is protected by U.S. rules that have long given people "the right to create reference guides that discuss literary works, comment on them and make them more accessible."

According to RDR, the book is based on material found on the fan-written Web site hp-lexicon.org.

The Center for Internet and Society was founded by Stanford law professor Lawrence Lessig. Its clients have included film documentarians, a Stanford scholar who battled with the James Joyce estate over her 2003 book about "Finnegans Wake" and musician Brian Transeau.