They had several cases along these lines involving several agencies, and I feel like people don’t understand the underlying legal idea - rule making power belongs to Congress. Federal agencies under the executive branch that have rule making powers receive those powers by Congress delegating it to them in a limited fashion through legislation.

Nitpick: rule making power does belong to executive agencies (at least until this SCOTUS decides to reverse Chevron deference). Law-making power resides solely with Congress.

What this means, as you suggest, is that Congress sets up statutory bounds within law, then the responsible executive agencies create rules interpreting them and defining how they’ll be enforced. Where cases like this one go wrong is when the agency oversteps the bounds of the law as passed by Congress. At that point, the agency has engaged in creating new law rather than rules, which is why the courts swat them down.

I agree with your overall gist, just feel that’s an important distinction to understand the situation.