> The laws should state something like "food purity should be within %x of yada yada, where x is updated yearly by the appropriate agency" Then it's up to the courts to decide if the law was broken or not.

This is kind of true, but also belies the depth of the Chevron change. In this example, plaintiffs can now, for example, challenge how the "X%" calculation is done. What's an appropriate methodology?

In the past, courts deferred to the agency: as long as it's scientifically valid + consistent, it's up to the regulator, not a judge. Now, it's up to a judge.

So if I sue and say "you should use a 0.01 alpha for calculations, not 0.05" for your X% calculation, then a judge makes the methodological decision, not the statistician.

IMO, it's not really reasonable for congress to design statistical methodologies as part of the text of a bill.