Re: Surely the people are sovereign
No one is saying the agencies can't create rules, in fact creating and enforcing rules is just what they are supposed to do. However, those rules have to be reasonably consistent with the laws passed by Congress.
One example is this whole kerfuffle over transgender people. When Congress passed Title IV in 1972 it was specifically to address discrimination against women. The current administration has written rules requiring schools and other organizations to treat biological men who "identify" as women as natural born women. Forcing these organizations to allow men into women's locker and rest rooms, along with competing against women in sports.
Not only is this grossly unfair to the women and girls, but it's also dangerous. Some of these claimed transgenders have evil intent and rapes have occurred, they are also bigger and heavier than natural women and have caused injuries.
Congress NEVER passed a law allowing that, it's certainly not a part of Title IV, if it was the bill never would have passed. The Executive Branch just decided that's what it wanted to do.
The Chevron decision was one that actually made a bit of sense at the time, it is logical that people in the agencies who were experts on some topic would write the rules. But like any human endeavor all too often you give someone a little bit of power and they can't help but abuse it.
That's what happed here, and that's why the ruling overturning Chevron was the right thing to do.