On Feb. 12 2026, the Trump administration revoked a scientific finding that long has been the central basis for U.S. action to regulate greenhouse gas emissions and fight climate change, the most aggressive move by the Republican president to roll back climate regulations.

The rule finalized by the Environmental Protection Agency (EPA) rescinds a 2009 government declaration known as the endangerment finding that determined that carbon dioxide and other greenhouse gases threaten public health and welfare.

The Obama-era finding is the legal underpinning of nearly all climate regulations under the Clean Air Act for motor vehicles, power plants and other pollution sources that are heating the planet.

The repeal eliminates all greenhouse gas emissions standards for cars and trucks and could unleash a broader undoing of climate regulations on stationary sources such as power plants and oil and gas facilities, experts say. Legal challenges are near certain.

The EPA also said it will propose a two-year delay to a Biden-era rule restricting greenhouse gas emissions by cars and light trucks. And the agency will end incentives for automakers who install automatic start-stop ignition systems in their vehicles.

The Supreme Court ruled in a 2007 case that planet-warming greenhouse gases, caused by the burning of oil and other fossil fuels, are air pollutants under the Clean Air Act. Since the high court’s decision, in a case known as Massachusetts v. EPA, courts have uniformly rejected legal challenges to the endangerment finding, including a 2023 decision by the U.S. Court of Appeals for the District of Columbia Circuit.

The endangerment finding is widely considered the legal foundation that underpins a series of regulations intended to protect against threats made increasingly severe by climate change. That includes deadly floods, extreme heat waves, catastrophic wildfires and other natural disasters in the United States and around the world.