I stumbled a bit on the phrase "puissance mandataire' while reading an article from Le Monde about the former Lebanese prime minister.
Ancienne puissance mandataire du Liban, la France a joué les médiateurs et le président français a invité à Paris M. Hariri et sa famille afin de tenter de sortir de l’impasse née d’une démission apparemment imposée par les autorités saoudiennes.
Former proxy power of Lebanon, France played the mediators and the French president invited Mr. Hariri and his family to Paris to try to break the impasse from a resignation apparently imposed by Saudi authorities.
I understand that France acquired a mandate over Lebanon after WWI. But how would you translate the phrase "ancienne puissance mandataire du Liban"? I'm having difficulty finding a suitable adjective. "Former mandatory power of Lebanon" makes no sense. But "Former proxy power of Lebanon" doesn't sound quite right.
A liberal translation is also possible, e.g. "Formerly having mandatory power over Lebanon, France has played the mediators..." But I'm much more interested in a simple and direct translation.