So they can only do this if they are somewhat certain that Bitcoin was in fact covered by existing legislation. I could imagine there's a good chance of successfully disputing this interpretation of the laws, considering the unique nature of Bitcoin.
we can't simply say "the unique nature of Bitcoin, GIVES us the right to do what ever the fuck we want" ...
that's just not coolOh I'm sorry if I gave you the impression that is what I meant - I'm absolutely for solid legal foundations for electronic cryptocurrencies! I just don't think Bitcoin is covered by current laws hence I would think any decision by a bank trying to classify it would be disputable under current legislation.
Ideally I would like to see new laws being crafted for cryptocurrencies after undergoing a public debate and normal democratic processes. Wishful thinking I guess...

we have to work with them, to define bitcoin in the law book.
Exactly!
The nature of Bitcoin had nothing to do with the decision. They found that MtGox was effectively operating as a money transfer business/bank by taking and holding user deposits of actual currency and that because they weren't licensed to do that they were operating outside the law. The issue being determined was whether they had a right to a French bank account. The ruling pretty much meant that because they weren't appropriately licensed for the services they were providing, the bank didn't have to provide them with services (and neither did any other French bank).
I thought that the nature of Bitcoin was indeed the issue here that had to be decided - if I may quote from Mark's OP:
Chances are it'll take a few weeks/months before a final decision is taken, however starting September 13th, a French court will review the question "Is bitcoin a virtual currency".
Are you talking about a different case or am I missing something?