The US Supreme Court ruled on Friday that courts must exercise independent judgment in assessing an agency’s statutory authority. This overruled the deference long afforded to an agency’s interpretation of its mandate under Chevron U.S.A. v. Natural Resources Defense Council.

The case of Loper Bright Enterprises v. Raimondo Secretary of Commerce considered the regulation of fishing. The petitioners challenged the decision of the National Marine Fisheries Service (NMFS) to require the petitioners to pay for observers required under a fishery management plan. They argued that the NMFS did not act within its mandate from the Magnuson-Stevens Fishery Conservation and Management Act (MSA).

The Supreme Court did not decide on the facts of Loper. However, these facts provided an ambiguity in legislation through which the court could overrule the Chevron deference and remand Loper for further proceedings. In Chevron, the court found that “the Administrator’s interpretation… is entitled to deference” when it involves technical and complex reasoning to reconcile conflicting policies. The Loper court disagreed, finding that “Chevron was a judicial invention that required judges to disregard their statutory duties.”

In reaching this conclusion, the court analyzed the Administrative Procedure Act (APA), legislation that determines the role of courts. The court found that the Chevron deference conflicts with the APA, which states that “the reviewing court” is to “decide all relevant questions of law.” The majority went on to discuss how the court has consistently minimized the Chevron deference’s scope over time–they hadn’t even used the principle since 2016–recognition that its “justifying presumption is… a fiction.”

The dissent attempted to defend Chevron deference by stating that judges must defer to agencies with institutional knowledge because “judges are not experts in the field.” However, the majority confirms that agencies’ statutory authority is a question of law, and, therefore, deference to agencies contradicts directly with the APA.

Though the court’s decision in Loper may contradict the stare decisis principle of judicial continuity, the court found that some cases must involve the court “correcting [its] own mistakes.” Despite this, the court still confirmed that the holdings of previous cases using the Chevron deference (including Chevron itself) stand, perhaps easing concern over a wave of new litigation over old issues.