I guarantee you a large majority of them don't read the rules anyway so any suggested change here would be largely meaningless, especially if you consider that if someone knew enough English to navigate to the rule section, they wouldn't need it. The servers are built around English-speaking only, people who choose to play here without a good understanding of English thereby a bad understanding of the rules must deal with any consequences that follow.
The only possibly meaningful change that could be made is changing the chat announcement that advises against non-English to different only (e.g. Anglais seulement!), but even then will it stop a significant amount of players from not speaking English, considering the factors of who will be reading chat announcements and who will willingly stop speaking (what is most likely) their native language?