"The police said they were astounded by how good the translation was. They said it was very professional."

As I am a professional translator, does that mean that you will be seeking my opinions of police work? I assume that they mean that it had been spellchecked and didn't contain any gross grammatical errors. It's not clear how much he had actually translated (if it was only the first three chapters I guess that's a plausible 10000 words or so) but if - as suggested elsewhere - http://www.iht.com/articles/ap/2007/08/08/arts/EU-A-E-BKS-France-Harry-Potter.php - he'd translated the whole thing he must have been working at a staggeringly impressive speed (a professional translator will normally be looking at doing something 2-3000 words a day, and although JKR's prose is not desperately challenging, spotting and reinventing made-up words and phrases in a foreign language is likely to slow anyone down), and is probably largely the product of some MT system, gawd help us (or the francophones at any rate).

There is, as far as I am aware, no law in France or anywhere else much against trying to translate anything you like for your own entertainment and/or edification, merely against distributing it. Of course it's obviously all about money, and the publishers' decision not to allow translation work to be started before the EN publication date is rather silly - although paranoia about the story getting out before the Big Day is just part of the highly successful hype around the whole Potter series - but even translators have to eat...