In one of the most highly anticipated decisions this term, the Supreme Court overturned a 40-year-old legal doctrine, so-called “Chevron deference,” under which judges had been expected to defer to a federal agency’s interpretation of laws that are ambiguous. The ruling, split 6-3 along ideological lines, will have far-reaching consequences, experts say, and could impact all sorts of federal policies, from health care and taxes to climate change. The cases at the center of this decision—Relentless, Inc.