"Authority" is generally the term used for how much power both the players and the GM are allocated to frame situations in various games, but I understand not everyone participates in the more esoteric game theory threads around here.
I'm not debating how true names should be used or not, I don't find it to be particularly compelling. (I know how I would use them if I wanted.) I'm just stating the players can't really DO anything with them without the DM formalizing some rules by fiat. Which would contrast with using banishment on a devil or demon, to illustrate the "formal authority" distinction. A player of the right class has explicit authority to cast banishment. The DM can, by either making a saving throw or some other fiat decision, explain why it doesn't work, but the player is empowered by the rules to try.