Man, I really wish the general public and reporters had some basic understanding of our constitutional system. The frantic fear mongering about the end of Chevron deference is driving me crazy.
Here's a primer for the uncertain.
The ruling only says judges do not have to give deference to an agency's own interpretation of its statutory authority when its authority to make a particular regulation is challenged. In short, it's solely the judiciary's job to determine whether a federal agency acted within the scope of its authority; the agency doesn't get to determine that on its own. And if the agency makes a persuasive case that it does have the authority, the courts can agree with it.
Nothing changes for cases where the agency’s authority to make a particular regulation is clear. Chevron deference only applied in cases where the question of authority was uncertain.
The ruling does not strike down any environmental laws or provide any basis for striking down any laws. It is entirely limited to the question of whether a particular executive branch agency regulation is authorized by one of those laws. It is limited to questioning agencies' statutory authority, not Congress's constitutional authority to make environmental, health, and safety laws.