Attorney General Phil Weiser challenges Trump administration’s rollback of Endangered Species Act protections

Sept. 9, 2026 (DENVER) – Attorney General Phil Weiser today joined a coalition of 21 attorneys general in filing two lawsuits to protect endangered and threatened species, one against the U.S. Fish and Wildlife Service and another against FWS and the National Marine Fisheries Service.

The lawsuits challenge new rules that gut essential protections for wildlife under the Endangered Species Act and threaten the survival of imperiled species. By making it easier for private companies or individuals to modify or degrade the habitats of listed threatened and endangered species, the rules leave these threatened species without core protections.

“Colorado is home to over 30 threatened and endangered species that are critical to stable and healthy ecosystems. The changes by the Trump administration put threatened and endangered species and their habitats at risk, undermining the comprehensive protections Congress mandated under the Endangered Species Act,” said Attorney General Weiser. “Our state is known for its great outdoors and responsible wildlife management. I will do everything I can to protect its wildlife and environment.”

The coalition’s first lawsuit challenges the federal government’s rescission of the longstanding regulatory definition of “harm.” Previously, the rule defined harm to include “significant habitat modification or degradation” that could kill or injure wildlife by damaging species’ natural habitats and behavioral patterns, including breeding, feeding or sheltering. Altering this definition reduces protections for habitats and makes it easier for them to be damaged or destroyed, even when that destruction ultimately threatens the survival of protected species.

The second lawsuit challenges two rule changes by FWS that reduce protections for threatened species and create a new process for designating areas as “critical habitat.” The first rule rescinds FWS’s regulations that automatically protect all newly listed threatened species. The second rule establishes a new process for designating areas as “critical habitat,” that will leave areas essential to species’ conservation without the protections that Congress intended.

Research shows habitat loss is the primary cause of species decline. In both lawsuits, Attorney General Weiser and the coalition argue the Trump administration’s rationale for gutting habitat protections is contrary to the intent of the ESA, which Congress enacted to protect endangered and threatened wildlife and the ecosystems they depend on for survival. In the second lawsuit, Attorney General Weiser and the coalition argue that FWS’s rescission of automatic protections for newly listed threatened species is contrary to the law’s conservation purpose because it leaves threatened species without protection necessary for their survival, substantially increasing the risk that they will become endangered. The coalition argues these rules are also contrary to the Administrative Procedure Act and National Environmental Policy Act.

Joining Attorney General Weiser in filing today’s lawsuits are the attorneys general of Arizona, California, Connecticut, Delaware, Hawaii, Illinois, Massachusetts, Maryland, Michigan, Minnesota, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, Virginia, Washington, Wisconsin, and the District of Columbia.

The complaints will be available on coag.gov/defending-colorado when filed.

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Media Contact:
Lawrence Pacheco
Chief Communications Officer
(720) 508-6553 office
lawrence.pacheco@coag.gov