text:  In a major win for the conservative legal movement, the Supreme Court on Friday reversed a decades-old ruling that put a thumb on the scale in favor of federal agencies. This is a landmark decision upending four decades of jurisprudence, a doctrine known as Chevron deference. It was named after the oil and gas company that had a key environmental case before the court 40 years ago. In overturning Chevron, Chief Justice John Roberts says courts should no longer defer to a federal agency's reading of an ambiguous statute.