A Sept. 14 Fish and Wildlife Service memo went beyond July's habitat rule, and the legal fight now covers both, with species from Texas prairies to the Northern Rockies in the balance.

Developing Story Note: This report covers new developments involving federal changes to Endangered Species Act enforcement. Information may change as courts and agencies act. Latest verified legal action reviewed: a supplemental complaint filed Oct. 1, 2026, by the Center for Biological Diversity and allies.

Conservation groups have widened their court fight against the Trump administration's Endangered Species Act changes. A supplemental complaint filed Oct. 1 challenges a Sept. 14 memo from Fish and Wildlife Service Director Brian Nesvik that limits the law's prohibition on "take" to acts intentionally directed at a listed animal.

That memo went further than the July rule rescinding the regulatory definition of "harm," which removed habitat destruction from what the agencies treat as prohibited harm. NOAA Fisheries has issued a similar memo.

The practical question for property owners, farmers and developers is what is now legal and for how long. For species already down to a few hundred animals, the question is whether losing habitat protections changes their odds of recovery.

A Rule, a Memo and Two Waves of Lawsuits

For nearly 50 years, federal regulations defined "harm" as an act that actually kills or injures wildlife, including significant habitat modification or degradation. The Supreme Court upheld that reading in 1995. The Interior and Commerce departments finalized a rule rescinding that definition on July 10, and it took effect Sept. 14.

Nesvik's memo, issued the same day, tells staff that take requires an affirmative act purposefully aimed at a particular animal. Under that reading, incidental deaths from logging, development or vessel traffic would generally fall outside the take prohibition. Critics note that both the rule and the memo rely on Justice Antonin Scalia's dissent in the 1995 case. Nature World News previously reported on how the July rule could reshape habitat conservation and on the end of automatic protection for newly listed threatened species.

The administration describes the change as restoring the law's text — not removing core protections. In a July 10 announcement, Interior said the old definition interfered with private property rights, and that existing permits and incidental take statements remain valid. Interior Secretary Doug Burgum said the action "restores common sense, respects private property, provides much-needed certainty for landowners."

Opponents are in court on several tracks. On Sept. 9, a coalition of 21 attorneys general filed two lawsuits in the U.S. District Court for the Northern District of California challenging the harm rescission and rules on threatened species and critical habitat, Washington's attorney general announced. Conservation groups represented by Earthjustice added the memo to their existing case. Noah Greenwald, endangered species co-director at the Center for Biological Diversity, called the memo "the most serious attack on imperiled animals" since the law passed more than 50 years ago.

Species on the Line, From Texas to the Rockies

Federal officials estimate that about 200 Attwater's prairie chickens remain in Texas, down from roughly 1 million a century ago, Harvest Public Media reported. Less than 1 percent of their coastal prairie survives. Dan Reinking, a senior biologist at the George Miksch Sutton Avian Research Center in Oklahoma, compared species at that level to intensive care patients and warned of a broader conservation crisis.

In the Northern Rockies, about 300 wolverines remain in the contiguous United States, and conservation groups sued earlier this year after the Fish and Wildlife Service missed its deadline to designate critical habitat, according to Montana Free Press. The Canada lynx's critical habitat was revised in a final rule to about 14,030 square miles in Colorado, Idaho, Montana and Washington, a 32 percent reduction from 2014.

Plants and insects are also part of the picture. Mead's milkweed is threatened largely because tallgrass prairie has been converted, said Missouri Botanical Garden conservation geneticist Christine Edwards, who is not part of the litigation. The western bumble bee, which the Fish and Wildlife Service found in 2016 may warrant protection, declined an estimated 93 percent between 1998 and 2018 but has not been listed.

Landowners Gain Certainty for Now, with a Legal Asterisk

For ranchers, farmers, timber owners and small developers, the immediate effect is fewer situations where habitat changes alone can trigger a take violation. Interior says that reduces permitting and compliance costs. Federal agencies must still consult under Section 7 on actions that could jeopardize a listed species or damage designated critical habitat, so projects needing federal permits or funding still face review.

The changes are not settled law — and that cuts both ways. Brigit Rollins, a staff attorney at the National Agricultural Law Center, said the reliance on a Supreme Court dissent is unusual and that frequent rule changes complicate business planning. If a court vacates the rescission or the memo, standards could change again during multi-year projects.

Scientists widely identify habitat loss as the leading threat to biodiversity, but researchers have not yet measured how these specific policy changes will affect individual populations, and that effect will depend on enforcement and future court rulings.

The Next Moves in Court

Landowners with pending permits or habitat conservation plans should confirm with their regional Fish and Wildlife Service office how the changes apply. State wildlife laws are unaffected and may still protect habitat. Residents who want a say can follow the Harvard Environmental and Energy Law Program tracker and comment on future species rules.

Next, federal judges in California and Washington state will set schedules on the challenges. A Fish and Wildlife Service status assessment for the Arctic grayling is due by February 2027.

Developing Story Timeline

Oct. 1, 2026: Conservation groups file a supplemental complaint challenging the Nesvik memo.

Sept. 14, 2026: The harm rescission takes effect, and Nesvik issues the take memo.

Sept. 9, 2026: Twenty-one attorneys general file two lawsuits.

July 10, 2026: Interior and Commerce finalize the harm rescission.

The bottom line: the changes are in effect, and lawsuits will decide whether they last.

What Readers Want to Know

What changed in September? The harm rescission took effect Sept. 14, and a same-day Fish and Wildlife Service memo limited take to acts intentionally aimed at a listed animal.

Is it now legal to kill an endangered animal? Intentionally killing or injuring a listed animal remains prohibited. The dispute centers on incidental deaths and habitat loss.

Who is suing? Twenty-one state attorneys general, plus conservation groups including the Center for Biological Diversity, Sierra Club, and WildEarth Guardians.

Do landowners still need federal permits? Existing permits remain valid, and federal projects still require Section 7 consultation. Check with your regional Fish and Wildlife Service office.

When will courts rule? No ruling dates have been set in the cases reviewed.