French term (edited): succursale l�gale fran�aise

I'm not just trying to be awkward. Here's my reasoning (to try and put it all in comments to the above would be too confusing):

I would use "branch" regardless of the type of business. That was the standard practice in the tax advisory firm I started out translating in (a "succursale" isn't necessarily an "agence" for instance, here it's referring to the type of establishment from a tax/legal point of view).
Not subsidiary because that is not the same thing; not permanent establishment because that covers subsidiaries too - here's an informative page I found
http://www.russell-cooke.co.uk/news_articles_3typesbusiness....

Finally, the only reason I wouldn't say "French legal branch" is because it could sound like a division of the company that handles legal affairs, and I think here it means "set up in compliance with the law", or "lawfully established" as Carolyn says.