It's not just majority rules, but there certainly doesn't need to be an official authority. If a style has an origin, and a tradition follows that origin and is perpetuated by a common usage, isn't that good enough? Just because there are hybrids or outliers wont change what seems obvious to me, at least, that NY style is an authentic, tradition-defined category of pizza. People who were raised on that tradition and care about it will want, rightly so, to defend it.
Do we need an authority? If so, look to those who come from and are part of that tradition. Will someone from that tradition step forward and claim SD to be a part of that tradition?