Typically, authority is
in respect of something-or-other.
What does the D&D referee have authority over?
Not what time the game starts. That's an issue of social consensus.
Not over who joins the group. That's an issue of social consensus.
Not over which rules the group uses. That's an issue of social consensus - eg if the GM tries to apply a rule and others reject it, the dispute has to be resolved just like any other dispute among people playing a game together.
The GM does have authority over what is written in their notes. But until that somehow comes into play at the table, it is just solitary authorship of fiction.
The relevant authority, as best as I can tell, is
authority over some parts of the shared fiction? Which parts of that fiction, in particular, is the key question. And that it be
shared fictionis a key requirement: if the GM specifies something about the fiction, and the game breaks up over it, then I think it's fair to say that the contentious fact never became part of the shared fiction!
GM authority over most of the backstory is the norm for D&D. But that is completely different from authority over outcomes!
Who has authority over
setting and
backstory? Who has authority over
situation? (ie where are the PCs and what is going on that calls the players to declare action)
And who has authority over the
outcomes of declared actions, and how do those outcomes feed into new situations?
A sandbox answers only the first of these questions. But most of the action in this thread is about the latter two - ie
situations, and
outcomes.
Fully agreed. The D&D rulebooks are chockfull of action resolution mechanics.
There are RPGs in which the way of working out
what happens next is that someone - perhaps the GM, perhaps the player sitting to the left of the one who made the declaration - decides what that is. But those RPGs don't need hundreds of pages of class build rules, spell descriptions, rules for setting DCs, etc!
I think it's helpful to read
@hawkeyefan's post closely:
I see that quote as limited to times when the rules are somehow unclear. You have nominated a variety of situations in which the rules are unclear or incomplete.
I think it's also helpful to think about
principles. The GM is free, in a formal sense, to create a NPC who, like a variation on the Manchurian Candidate, will stonewall every attempt to interact or gain information unless the players declare that their PCs do some very specific thing. But is that really a good exercise of authority over backstory and situation? To me it looks like an attempt to control outcomes of action declaration, by declaring in advance that all but one of the salient declarations will fail.
Whether or not that falls within the bounds of the 5e rules in some literal sense, is it good GMing? Who would say so?