The conservative-led Supreme Court on Wednesday heard arguments in a case that threatens to severely restrict the regulatory authority of federal agencies on issues ranging from environmental protection to guns to healthcare. The case centers around the “Chevron deference,” a precedent established in 1984 which requires courts to defer to an agency’s interpretation of laws. Fishing companies are challenging the doctrine, long maligned by corporations and the right. The legal effort is backed by far-right interest groups including the network of billionaire Charles Koch. Liberal Justice Elena Kagan defended the practice, saying, “And it’s best to defer to people who do know, who have had long experience on the ground, who have seen a thousand of these kinds of situations.” Kagan added, “And, you know, judges should know what they don’t know.” A ruling by the Supreme Court is expected in the summer.