Author J.K. Rowling, pictured arriving in court in Manhattan in April, testified the unauthorized publication of a Harry Potter Lexicon would constitute 'wholesale theft' of her material. (Louis Lanzano/Associated Press)

A U.S. federal judge in Manhattan has sided with author J.K. Rowling and ruled against the publication of a Harry Potter encyclopedia created by a fan of the book series.

Rowling launched a lawsuit last year against Steven Vander Ark and his publishers, RDR Books. Vander Ark runs a popular Harry Potter Lexicon website.

Judge Robert Patterson said in his Monday ruling that the encyclopedia would violate Rowling's copyright and would cause her irreparable harm as a writer: "[The] Lexicon appropriates too much of Rowling's creative work for its purposes as a reference guide," said Patterson in his decision.

He permanently blocked publication of the reference guide and awarded Rowling and Warner Bros. Entertainment Inc. $6,750 U.S. in statutory damages.

Warner Bros. is the studio behind the Harry Potter films and owner of intellectual property rights to the Potter books and movies.

Rowling's seven Potter books have sold nearly 400 million copies worldwide and have been translated into 64 languages.

The case was fraught with competing emotions on both sides.

During testimony in April, the Edinburgh-based writer said the unauthorized book would simply be a "rearrangement" of her work and constitute a "wholesale theft of 17 years of my hard work."

She fought back tears as she stated: "These books, they saved me, not just in the very obvious material sense, although they did do that … I would have to say that there was a time when they saved my sanity."

Rowling was a single mom at the time she began writing the books.

Vander Ark, who has called Rowling his literary icon, was brought to tears when asked how the case has affected his reputation among the wider community of Potter fans.

"It's been difficult because there has been a lot of criticism … This has been an important part of my life for the last nine years or so," he said as he wiped away tears.

The ex-school librarian launched his website in the late 1990s and has since studied and posted information about the novels on the site, which Rowling herself admitted she enjoyed.

The author says the case has ruined her warm relations with Vander Ark.