The question “Can a Ranger's Fighting Style be a prerequisite for the feat Two-Weapon Defense?” highlights an apparent error in the French translation of the D&D 3.5e PHB. Is there an official statement from WotC (or TSR back in the 1e/2e days, for that matter) that the English text of the D&D rules materials is authoritative/normative? Or is it simply a (rather safe) assumption to make?
I certainly think so
Wizards of the Coast is an American company, its employees work in English, and the English versions of the books were the first published. The translations appear to have been sourced out, not done in house.[Citation Needed] So far as I can tell, errata has only ever been released by Wizards of the Coast for the English editions, which means that other translations, even if the translation was accurate, are now out of date.
For all of these reasons, and because of the occasionally-poor quality of translations, I feel it is reasonable to see the English translation as authoritative, for when authority is desired. The translations remain potentially-useful to those more comfortable in that language, as authority is not always the most important aspect of the rules at all tables.
Unless you are doing something like large-scale organized play that's open to the public, it doesn't matter if a ruling is official or not. What matters is what the GM and the players agree to. Because official rulings are not generally important for RPG play, WotC may not have a published policy on this.
WotC's other big game, Magic: the Gathering, is also written in American English and then translated into many other languages. Because MtG needs tight rules definitions to support tournament play, WotC's official policy is that the English card & rules texts are authoritative, and all translations are provided as a non-binding convenience for non-English-speaking players.
Officially authoritative or not, the English rules can definitely be taken as a better indication of the authors' intent than a translation since the books were originally written and edited in English.
If the rules are unclear or unbalanced in the French (or any other) translation, consult the English as an alternative. If you are still unsatisfied, ask someplace like here, or make a house rule that produces better results for you.