When you fly to France and want to land at an aerodrome where there is no tower or outside business hours, usually the official unicom language is French. Legally, one would have to get a ICAO language proficiency entry for French as well.
Can you point out a reference for this?
I can understand why it would make sense, but I've never seen any regulation with required it.
Indeed it would make French airfields in accessable to many foreign pilots even if they were fluent French speakers, simply because there is no facility to add French languange proficiency to their licence.
Imagine a Norweign pilot asking the Norweign CAA for a French Languange Proficiency test so that they could add it to their licence. It's very unlikely that they would have developed such a test, or have such an examiner.
Nobody other then the Norweign CAA can add any privlidges to a Norweign licence other than the Norweign CAA. Hence such a pilot could never visit such a French airfield.
I don't believe that there is any languange requirements in ICAO either other than needing either the local language or English.
Indeed many of these airfields can be used non-radio, making such a requirement simply silly.