Twenty US states and Washington, DC, sued US President Donald Trump’s administration on Wednesday, challenging new rules that they say weaken the federal Endangered Species Act. They said that the rules could allow development, mining and oil drilling in habitats of threatened wildlife.The lawsuits, led by Washington state, California, Maryland and Massachusetts, were filed in federal courts in the San Francisco area. They target rules issued by the interior and commerce departments less than two months ago that changed how the landmark 1973 law protects endangered species and their habitats.One lawsuit challenges a new definition of “harm” under the Endangered Species Act. The states say the change removes long-standing protections for wildlife habitats by allowing activities such as oil drilling and mining as long as they are not “directed immediately and intentionally” against particular animals, even if they result in injury or death.The states called the change a “reversal of staggering proportions”. They argue that the rules are “arbitrary and capricious” and violate the National Environmental Policy Act.The second lawsuit challenges two other changes. One removes broad protections for species newly classified as threatened unless the US Fish and Wildlife Service introduces protections specifically for that species. The other requires the government to consider objections from businesses, including potential economic costs, before designating areas as “critical habitats”.Washington attorney general Nick Brown said the administration was weakening a law that has protected wildlife for decades.“The Trump administration is trying to undermine the law, the will of Congress and the will of the people who overwhelmingly support protections for endangered species,” Washington attorney General Nick Brown said at a press conference. “Instead of stewardship, this administration’s approach to our land, to our water is one of exploitation.”The US interior department rejected the states’ claims and said federal agencies should implement the law according to its text.“The role of federal agencies is to faithfully implement the Endangered Species Act as written, not to expand its reach through interpretations favoured by advocacy organisations,” an Interior Department spokesperson said.“This lawsuit seeks to preserve a decades-old regulatory overreach that expanded the Endangered Species Act beyond the authority granted by Congress,” the spokesperson added. “The department will vigorously defend its authority to implement the law according to its plain text.”The Endangered Species Act, enacted by Congress in 1973, has been credited with helping save species including the California condor, grizzly bear and humpback whale. The states said 99% of the species protected under the law have avoided extinction.Wildlife advocates have long identified habitat loss as a major cause of extinction. New York attorney general Letitia James said the states were seeking to preserve protections for future generations.“We owe future generations a world where bald eagles soar, sea turtles swim and all wildlife thrives,” New York Attorney General Letitia James said in a statement.The Trump administration has argued that the law has been used to block development projects and impose costs on businesses. Interior Secretary Doug Burgum has said the Endangered Species Act has been weaponised to stop projects, hurt competitiveness and undermine national security.Burgum has said the new rules bring the law closer to its original intent.The changes come as the Trump administration seeks to reduce environmental regulations that it says constrain American businesses. The administration has also rolled back several environmental initiatives and reduced support for clean energy.The new rules followed a 2024 US Supreme Court decision that overturned a decades-old precedent requiring courts to defer to federal agencies’ reasonable interpretations of laws they administer.The latest lawsuits add to dozens of legal challenges filed by Democratic-led states against major policy changes during Trump’s second term. Environmental groups have separately sued to block the revised definition of “harm”.