 So Chevron deference required federal courts to defer to these agencies' interpretations of ambiguous laws as long as those interpretations were reasonable. And what that means, basically, is that Congress can't foresee every possible application of the laws that it writes. It can't foresee the gaps or ambiguities that might arise. And so for 40 years, the courts said, well, you know what? These agencies are filled with experts. They're filled with civil servants, with scientists,