It's not my meaning and I don't see the entailment, prima facie or otherwise.That would on-surface entail that GM-power is not feasible. Is that your meaning here?pemerton said:If you mean that rule zero expresses a commitment, by participants, to follow one particular participant in setting the rules of the game, then the question becomes: is such a commitment actually feasible? And the answer, in the context of a social pastime (cf a tournament or other institutional contex) is No.
Admittedly, I'm not 100% sure what you mean by "GM power", but I take it to mean the GM's capacity to add to the shared fiction. The GM has that power the same as any other participant does: the GM can offer suggestions and the other participants can accept them.
Rules can mediate acceptance of suggestions. They do this if everyone agrees to them. That agreement is (in informal, purely social contexts) voluntary. No one can be bound to agree. They can withdraw their agreement at any time.
Someone, including the GM, can propose a new rule - that is, a new way of mediating acceptance of suggestions. That proposal can be accepted or rejected. But the GM can't have any particular power in this respect. (Cf, eg, a tournament organiser.) In this sort of informal context there is no scope for (what Hart would call) secondary rules eg rules of change. (And as Hart explains, introducing such rules is part of a process of institutionalisation.)