On April 17, 2025, the U.S. Fish and Wildlife Service (“USFWS”) and the National Marine Fisheries Service (“NMFS”) (collectively the “Services”) published a notice in the Federal Register of a proposed rulemaking that would rescind the regulatory definition of “harm” under the Endangered Species Act (“ESA”). The ESA prohibits “take” of threatened and endangered species. The statute defines “take” to include actions such as: “harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.” The ESA does not define “harm,” but the USFWS’s existing regulations define “harm” as “an act which actually kills or injures wildlife . . . [which] 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.” NMFS’s definition is materially the same.

Since the USFWS adopted its regulatory definition of “harm” over four decades ago, there has been significant litigation regarding whether and to what extent actions that modify habitat constitute “harm” under the regulatory definition. Notably, in 1995, the U.S. Supreme Court upheld the USFWS definition of “harm” in Babbitt v. Sweet Home Chapter of Communities for a Great Oregon, 515 U.S. 687 (1995). In Babbitt, the Supreme Court relied on Chevron USA v. National Resources Defense Council,467 U.S. 837 (1984), a case that generally required courts to defer to federal agencies’ regulatory interpretations of statutes,to conclude that the USFWS interpretation of “harm” was reasonable.

In 2024, however, the U.S. Supreme Court overturned Chevron in Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024). In Loper Bright,the Supreme Court rejected the principle that resolution of statutory ambiguities requires courts to defer to agencies and determined that courts, rather than agencies, are better suited for interpreting congressional meaning in statutes.

In the proposed rule, the Services cite to Loper Bright as a source for eliminating their definition of “harm,” concluding that the existing regulation does not match “the single, best meaning of the statute.” The proposed rule also relies upon Justice Scalia’s dissent in Babbitt, in which Justice Scalia asserted that applying the rule of statutory interpretation, noscitur a sociis (i.e., “known by its associates”), the nine other verbs under the statutory definition of “take” all require an affirmative act against a particular animal rather than actions, such as the modification of habitat, that indirectly injure a population of animals, and “harm” should be interpreted similarly. In the proposed rule, the Services refer to Scalia’s discussion of noscitur a sociis. The Services then go on to conclude that, with Chevron overruled, the definition of “harm” is being rescinded because it is not “the single, best meaning of the statutory text.”

The Services will accept public comment on the proposed rulemaking through May 19, 2025. The proposed rule notes that if the proposed rulemaking becomes final, the revision would be “prospective only” and would not impact permits already approved at the time the regulation is finalized. The proposed rule also notes that the change would not alter the statutory definition of “take,” which includes “harm” and “harass.”