The U.S. Fish and Wildlife Service and National Marine Fisheries Service (the “Services”) recently finalized a significant Endangered Species Act (ESA) rule that rescinds the regulatory definition of “harm” (the “Final Rule”). The Final Rule, published on July 14, 2026, becomes effective September 14, 2026.

For more than 40 years, federal regulations defined “harm” to include significant habitat modification that actually kills or injures listed wildlife by impairing essential behavioral patterns such as breeding, feeding, or sheltering. In Babbitt v. Sweet Home Chapter of Cmtys. for a Great Or. (Sweet Home), the U.S. Supreme Court upheld the regulatory definition of “harm” as a permissible interpretation of the statutory term “harm,” which is part of the statutory definition of “take.” 515 U.S. 687 (1995).

The Final Rule removes the regulatory definition entirely. According to the Services, the ESA’s statutory definition of “take”—which includes actions such as harassing, harming, pursuing, hunting, shooting, wounding, killing, trapping, capturing, or collecting listed species—is sufficiently clear, and thus, the additional regulatory definition of “harm” is inconsistent with the ESA. The Services further explained that, by defining “harm,” they improperly expanded the ESA beyond its text and implied that certain forms of habitat modification are a prohibited “take.”

What Does This Mean for Project Development?

Although the regulatory change is significant, its practical effect may not be immediate for many project proponents.

Federal agencies must still comply with section 7 of the ESA when authorizing, funding, or carrying out federal actions, including the obligation to avoid jeopardizing listed species and destroying or adversely modifying designated critical habitat. Likewise, many existing biological opinions, incidental take statements, and habitat conservation plans remain in place. The Final Rule primarily affects how the Services interpret the section 9 prohibition on “take,” particularly where alleged impacts arise solely from habitat modification rather than direct injury to listed wildlife.

For water providers, irrigation districts, municipalities, developers, and infrastructure owners, the Final Rule may ultimately influence permitting strategies and ESA compliance analyses, particularly for projects involving land management, reservoirs, canals, pipelines, and other facilities with potential habitat impacts.

Litigation Is Almost Certain

The Final Rule is unlikely to be the final word.

Environmental organizations filed a suit almost immediately after publication of the Final Rule, arguing that the rescission conflicts with both the text of the ESA and the Supreme Court’s decision in Sweet Home. The plaintiffs contend that Congress intended the ESA to prohibit habitat destruction that results in injury or death to protected species and that eliminating the longstanding regulatory definition is arbitrary and contrary to established precedent.

The Services, by contrast, maintain that the prior definition represented an unauthorized expansion of the ESA and that the rescission restores the statute’s plain meaning.

As the litigation proceeds, entities undertaking projects with potential impacts to listed species or their habitat should continue to evaluate ESA obligations carefully and remain attentive to further judicial and regulatory developments.

For questions or additional information, please contact:

• Ryan J. Mitchell, rmitchell@somachlaw.com

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