By Taylor Strain and Austin C. Cho

On April 17, 2025, the U.S. Fish and Wildlife Service (USFWS) and the National Marine Fisheries Service (NMFS) (collectively: the Services) published notice of a proposed rule in the Federal Register that would rescind the current definition of “harm” to species under the Services’ federal Endangered Species Act (ESA) regulations.

Background

Enacted in 1973, the ESA is a federal statute designed to conserve species of wildlife, fish, and plants that are considered endangered or threatened. (16 USCA § 1531.) Among the ESA’s key provisions is a list of prohibited acts, which makes it unlawful to engage in certain conduct involving endangered species of fish, wildlife, or plants. (16 USCA §§ 1538, 1533.) For example, the ESA prohibits the sale or offer for sale of listed species in interstate or foreign commerce, as well as their import into or export from the United States. (16 USCA § 1538.) The statute also prohibits the “take” of endangered fish or wildlife, either within the United States, the territorial waters of the United States, or the high seas. (16 USCA § 1538.) The ESA defines “take” to mean “harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.” (16 USCA § 1532.)

Both USFWS and NMFS have issued regulations defining harm as it is used within the ESA definition of “take” to include harmful modifications to habitat. USFWS defines harm as “an act which actually kills or injures wildlife” in a manner that “may include significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding, or sheltering.” (50 CFR § 17.3.) NMFS uses a similar definition that encompasses “significant habitat modification or degradation which actually kills or injures fish or wildlife by significantly impairing essential behavioral patterns, including, breeding, spawning, rearing, migrating, feeding or sheltering.” (50 CFR § 222.102.) Thus, under both regulatory definitions, take is interpreted broadly to include indirect and unintentional harm to species that may be caused by changes to habitat.

The Proposed Rulemaking

In the recent Federal Register notice, the Services propose to rescind the definitions of harm contained in their respective regulations. (90 Fed. Reg. 16102 (Apr. 17, 2025).) The Services explain that the current interpretation of harm—originating in regulations upheld by the Supreme Court in Babbit v. Sweet Home Chapter of Communities for a Great Oregon (Sweet Home) 515 U.S. 687 (1995), “do not match the single, best meaning” of the ESA. (Id. at 16103.) In Sweet Home, the Supreme Court upheld the USFWS regulation defining harm based on the deference afforded to agencies under Chevron, U.S.A., Inc. v. Natural Resources Defense Council, Inc., (Chevron) 467 U.S. 837 (1984), and the Secretary of the Interior’s discretion in construing the intent of Congress when defining the term harm under the ESA. (515 U.S. at 708.) But last year in Loper Bright Enterprises v. Raimondo, (Loper Bright) 603 U.S. 369 (2024), the Court overruled the longstanding precedent of Chevron deference, holding that agency regulations must conform to the governing statute’s “single, best meaning.” (See 90 Fed. Reg. at 16103 [quoting Loper Bright, 603 U.S. at 400, 406].) In lieu of granting Chevron deference, the Supreme Court analyzed whether “the statute authorize[d] the agency action.” (Id.)

Relying on the Dissent in Sweet Home

The Services cite the dissent in Sweet Home to support their position that the current definition of harm does not match the single, best meaning of the ESA. That dissent argued that even under Chevron, a definition of harm that included indirect effects was untenable. (Id. [citing Sweet Home, 515 U.S. at 715].) The Services’ notice emphasizes that “take” should be limited to actions that “reduce those animals, by killing or capturing, to human control.” (Id. at 16103 [quoting Sweet Home, 515 U.S. at 717].) Under the interpretive cannon noscitur a sociis—the principle that a word is known by the company it keeps—the term harm, like the nine other verbs in the definition of “take,” is better understood to connote an “affirmative act []… directed immediately and intentionally against a particular animal,” not merely indirect or accidental injury to a population of animals. (Id. [quoting Sweet Home, 515 U.S. at 719-20].)

Existing Definitions of Harm are Erroneous

Following Loper Bright, the Services conclude that the existing definitions of harm violate established interpretive canon, disregard centuries of legal history, and conflict with the structure of the ESA. (Id. at 16103.) They also state that a replacement definition is unnecessary, given the statute’s comprehensive definition of the term “take.” Further elaboration on a single component—i.e., “harm”—is, in the Services’ view, therefore superfluous. (Id.) The Services distinguish the holding in Sweet Home by characterizing the prior definition of harm as a permissible interpretation, but not the only possible one. Thus, the proposed rescission is consistent with Sweet Home, particularly in light of Loper Bright’sabrogation of Chevron deference. (Id.)

Conclusion and Implications

With the removal of deference to agency interpretations in Loper Bright, the Services propose to rescind their regulatory definitions of “harm” to ensure that their respective definitions conform to the single, best reading of the ESA. The Services accepted public comments on the proposed rule until May 19, 2025. The Federal Register notice remains available at the following link: https://www.govinfo.gov/content/pkg/FR-2025-04-17/pdf/2025-06746.pdf