The Trump Administration's effort to strip away protections under the Endangered Species Act that had previously been upheld by the Supreme Court. The Administration seems to think they're entitled to ignore that earlier decision because it was decided under the Chevron test and Chevron has since been overruled. They're wrong. If it wishes to change the existing interpretation, the agency must give a reasoned argument for doing so that discusses the relevant policy issues, including reliance and the impact of its decision on endangered species.