Every ecosystem has a “keystone” species whose presence or absence affects everything else in the landscape. The legal system works in a similar way.
A series of recent U.S. Fish and Wildlife Service changes aimed at the Endangered Species Act appear to consider the 1973 law as the keystone to unleashing resource development, according to both federal agency leaders and environmental activists challenging the Trump administration policies in court. In particular, they warn that a rule changing the definition of a single word in the ESA could effectively gut it.
“They’re coming for the Endangered Species Act from multiple directions,” said Earthjustice attorney Tim Preso, who is representing a coalition of environmental groups challenging the rule change. “This is about pulling away the safety net from the most imperiled wildlife in service of their deregulatory agenda.”
Ever since its passage, the ESA has created tension between the needs of imperiled animals and plants and the desires of humans seeking to use the same landscape. The law protects those species from extinction mainly by prohibiting their “take,” a legal term meaning to put under human control. The word “take” was defined as “harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect.” Within that list, the word “harm” meant “significant habitat modification or degradation where it actually kills or injures wildlife.”
A Federal Register notice that took effect on Sept. 14 rescinded the ESA’s definition of “harm” in the list of words defining “take,” something the Trump administration had sought since the early 2025. It redefined “take” to mean “only an affirmative act that is intentionally and purposefully directed at a particular animal.” Finally, it advised that “only action directed at living animals constitutes a ‘take,’ so destroying [essential] habitat …would not violate the Act,” adding “modification of unoccupied habitat is never a take, however certain its eventual effect on the species.”
The word “take” forms the heart of the ESA’s protective power, according to an analysis by University of Montana law professor and ESA expert Sandra Zellmer.
“Habitat modification is the primary reason for [ESA] listing,” Zellmer wrote in her 2026 American Bar Association journal paper. “If modifying habitat is no longer a ‘take,’ the ESA itself would be rendered incapable of satisfying Congress’ goal: ‘to halt and reverse the trend toward species extinction, whatever the cost.’”
While the “take” rule has earned lots of attention in recent days, it’s far from the only ESA change in the works. Preso listed several more federal actions aimed at dismantling ESA authority.
For example, he noted FWS also plans to revoke what’s known as the “blanket rule” which gives ESA-listed threatened species the same level of protection as endangered species while more tailored recovery plans are under development. And the Forest Service’s recent intention to repeal the Roadless Rule could undermine ESA protections for listed grizzly bears, because federal grizzly recovery plans depend on the bears having roadless habitat for security.
Trump executive orders issued in 2025 also targeted the ESA as an impediment to energy development. Many of those concerns have been wrapped into a congressional bill for widespread permitting reform of energy and infrastructure projects, which is nearing final passage this fall. In an email, Western Environmental Law Center spokesman Erik Schlenker-Goodrich told Mountain Journal in an email the bill would “prove to be the largest rollback of environmental and public health protections in U.S. history, weakening the Clean Water Act, Endangered Species Act, National Environmental Policy Act, and more.”
Endangered species fall under the oversight of multiple agencies within the departments of Interior and Commerce. Those in turn impose ESA regulations on other federal, state and private stakeholders, including the U.S. Forest Service and Bureau of Land Management, state wildlife agencies, and ranchers, farmers, miners and loggers.
Asked for comment on the September imposition of the rule, an Interior press official only provided a July 10 press release from Interior Secretary Doug Burgum and Commerce Secretary Howard Lutnick stating the move terminates an outdated regulation that caused years of federal overreach.
“For years, federal agencies abused the ESA to obstruct lawful land use and burden American families and businesses,” Burgum said in the release. “That approach turned routine activity into a regulatory trap, drove up costs that impacted people’s lives, and expanded federal authority beyond what Congress intended. This action restores common sense, respects private property, provides much-needed certainty for landowners and follows the statute Congress actually passed.”
Noah Greenwald of the Center for Biological Diversity, which Earthjustice is representing against the federal government, claimed the Fish and Wildlife Service is throwing out the landmark environmental legislation.
“It’s a radical departure from how the ESA has been interpreted and implemented for more than 50 years,” Greenwald said. “I would say it’s a ‘scorched earth, we don’t care anymore’ policy.”
Greenwald added that while the change was likely to spend years in court, actual damage to ESA-protected species could happen much faster. Animals that depend on pristine habitat, such as bull trout or spotted owls, could disappear as logging or mining projects win approval without ESA consultations under the new rules, he said.
Few organizations have commented openly in support of the change, or have heralded its passage. One, the Association of General Contractors of America, posted its argument favoring the rescission on its website, stating the “prospect of take (including incidental take) of a species or destruction of habitat is a significant risk and concern for construction contractors … AGC appreciates the administration’s efforts to reduce unnecessary regulatory burdens – especially for the recognition that take or harm implies an intention or affirmative act.”
President Richard Nixon signed the Endangered Species Act in 1973, and the U.S. Fish and Wildlife Service published its first definition of the word “harm” in 1981, declaring it meant “significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding or sheltering.” The Supreme Court upheld that definition in a 1995 case, Babbitt v. Sweet Home.
On the losing side of that decision, Supreme Court Justice Antonin Scalia’s dissenting opinion essentially mashed all the “take” nesting dolls together under a legal principle known as noscitur a sociis: “a word is known by the company it keeps.” The other definitions of “take” all referred to direct injury to a specific animal, in Scalia’s reasoning. “Harm” improperly added indirect injuries to the definition, which allowed federal agencies to create unfair regulations about land use.
On the winning side, six justices agreed that the word “harm” in endangered species management specifically referred to habitat modification. The majority ruling also directly rejected Scalia’s noscitur a sociis argument, noting that if all the words meant the same thing, there was no point in using so many different ones.
That opinion held until a 2024 Supreme Court case opened the door for the rule change, according to an Ohio State University analysis. Loper Bright v. Raimondo overturned the Sweet Home decision by getting rid of another Supreme Court precedent known as “Chevron deference.” For decades, Chevron deference required judges to accept an agency’s opinion or policy if the congressional law was ambiguous or the agency’s response was reasonable. The majority in Loper Bright held instead that judges should make those determinations based on who made the best argument in court. The Trump administration took that a step further.
“According to the agencies, [Loper Bright] left open the possibility that the executive branch could … depart from regulations that do not match the single, best meaning of the statute,” the OSU analysis stated. “This, coupled with Scalia’s dissent in Sweet Home, is the agencies’ basis for rescinding the definition of “harm.”
“The Services are persuaded instead by Justice Scalia’s analysis as to what the correct construction of the statutory text is,” FWS stated in its Federal Register publication. “The Court left open the possibility that the executive branch could itself depart from regulations that do not match the single, best meaning of the statute — so long as the new regulations reflect that best meaning.”
In the Sept. 14 legal guidance memos, Interior and Commerce officials explained the new rule clarifies that unintentional “take” was no longer a concern of the ESA. In an example, the memo said someone draining a pond to kill a turtle would be breaking the law if the person deliberately wanted to “take” the turtle. “When that purpose is absent, there is no take, however serious the resulting injury may be. A vessel that inadvertently strikes a whale has not taken it, because the vessel’s course was not set against the whale.”
Preso called that “180 degrees opposite” of what the ESA has meant since 1973. “And not only are they picking their own interpretation,” he told Mountain Journal, “they’re picking the one rejected by a majority of the Supreme Court when it was before the Supreme Court. Everything’s upside-down.”
The rule change received about 358,000 public comments, according to its Federal Register tally. FWS declined requests to hold public hearings and extend the 30-day review period on the proposal.
The CBD lawsuit is one of at least seven filed since the Trump administration changed the definition of the word “take” in its interpretation of how the federal government oversees the habitat used by endangered and threatened animals and plants. Other challengers include two Native American tribes, a coalition of 21 states, and numerous environmental organizations. Most suits were filed in July, shortly after the rule change was finalized in the Federal Register. The federal government has until early October to respond.
