I think it is more of a case where the agency was set up for one goal, but then later the agency created additional goals that were greater in scope than the original goal.
The way I read the decision is that an agency may refine, and even move the goal posts some, but when the goal posts are no longer in the stadium, then they have gone too far. Congress is the only one authorized to create a bigger stadium.
I am not sure that the FAA has moved the goal posts out of the stadium like the EPA. And, in my opinion, the ATF and ICC.
But, to keep the conversation on aviation, maybe the FAA has exceeded it's authorization as it relates to space flight. Does anybody know if space flight has been delegated to the FAA, or did they just grab it.