Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,182
I believe the "law" is that you must be able to speak either English or the local language.
YMMV, as your Air France example showed how attendants can make things up if they wish, but you are unlikely to be kicked out of your seat if you are mobile (i.e. not in a wheelchair or wearing a cast for a broken leg) and speak English fluently.