Well, it is a case of unauthorized Localization gone wrong:

PARIS (Reuters) - Police arrested a teenager suspected of posting his own translation of the latest Harry Potter novel on the Internet weeks before the official French release, the book’s publishers said on Wednesday.

The 16-year-old schoolboy, from the Aix-en-Provence region in southern France, was taken into custody by a police anti-counterfeiting unit and later released, said a spokeswoman for the Gallimard publishing house, which handles the French editions of the novels.

I wonder if it the translation was any good?

Full Story from Reuters: Police arrest French teen over Potter translation