Sorry I guess my intent wasn't clear - I was basically relating that I don't understand why people think this decision is a catastrophe, because clearly the agencies were able to function before the ruling, so claiming things will break when we went back to the earlier state, clearly can't be catastrophic.
I generally avoid this thread these days for my own sanity, but a quick response here relating to the effects of the decision.
Chevron deference meant that, in a situation where a statute was ambiguous (which is very often the case, and often intentionally so to avoid congressional responsibility) a court will give an agency deference on its interpretation of said statute. Not a blank check however, as when an agency takes an 'arbitrary and capricious' stance that doesn't fly.
A good chunk of the motivation behind this was that agency staff are trained experts in a policy area, while judges may not be. (For an example of where judicial non-expertise has been a recurring problem, see how it's handled patent law over the decades.)
This sounds like a lot of deference, and it can be, but courts have routinely ruled that a given statute isn't ambiguous or an agency was acting arbitrarily and capriciously. (Some presidential administrations have had a lot more trouble passing this test than others.)
Now, however, a court will be giving an agency no deference. What this means in practice is that a court will be more free to decide an agency action is incorrect, meaning less completed agency action overall. On paper this would sound like favoring the right more than the left, as the right tends to have the position of less agency action overall, but in practice this is isn't very accurate. There are still hundreds or thousands of laws that
require agency actions to implement, and even beyond that both parties commonly use agency action to drive their desired policies.
My personal prediction is that this will ultimately result in less policy change and development writ large up and until congress gets more active and precise in its legislating - not something I'd bet on happening anytime soon.
There is, however, the additional wrinkle in today's decision (not
that one, one of the other ones) that effectively gets rid of the statute of limitations for challenging an agency action under procedural grounds. Combined with the Chevron case you could see more overruling of existing rules and thus lead to less overall existing regulation.