A judge says “Harry Potter” author J.K. Rowling has won her claim that a fan violated her copyright with his plans to publish a Potter encyclopedia.

Judge Robert Patterson said in a ruling Monday that Rowling had proven that Steven Vander Ark’s “Harry Potter Lexicon” would cause her irreparable harm as a writer.

Rowling sued sued Michigan-based RDR Books last year to stop publication of the lexicon. Vander Ark runs the popular Harry Potter Lexicon Web site.