[overlordalex]

Yes and no. If congress has granted the EPA authority to regulate water to ensure it's not bad for you, then someone needs to determine what "bad for you" means.

Previously, under Chevron, the courts would defer to the EPA as the experts to make that determination (with the understanding that congress could always pass more specific legislation if they felt the EPA was overstepping its granted authority)

What the Supreme Court has said is deferring to the agency is going too far, and that if congress wants specific things regulated then it needs to be specific in it's legislation. Prima facie that makes sense, except for two major problems: congress is not productive enough in passing legislation, and congress are not the experts

This means that when questions like this arise, it comes to the courts to be the ones who end up interpreting the statutes and making the determination on what "bad for you" means.