The administration of Donald Trump has repealed the 2009 “endangerment finding,” a scientific determination that greenhouse gas emissions threaten human health.

Axar.az reports, citing Reuters, that his finding, originally adopted under Barack Obama, formed the legal basis for federal regulation of greenhouse gases under the Clean Air Act.

With the repeal, the Environmental Protection Agency (EPA) has also eliminated federal tailpipe emissions standards for cars and trucks. The administration argues that the previous interpretation of environmental law was flawed and outside statutory authority, calling the move the largest deregulatory action in U.S. history. Officials claim it will save taxpayers $1.3 trillion.

The endangerment finding was strengthened after the 2007 Supreme Court ruling in Massachusetts v. EPA, which confirmed the EPA’s authority to regulate greenhouse gases. Its repeal removes federal requirements to measure and limit emissions from vehicles, though power plants may not immediately be affected.

Supporters, including coal industry representatives, say the move will reduce regulatory burdens and protect energy reliability. However, environmental groups strongly oppose the decision, arguing it will increase pollution, worsen climate impacts, and raise long-term costs for consumers. Several organizations, including the Natural Resources Defense Council, have pledged to challenge the repeal in court, likely triggering prolonged legal battles that could reach the Supreme Court.

The rollback marks the most sweeping U.S. climate policy reversal of the current administration and further distances the U.S. from prior climate commitments, including withdrawal from the Paris Agreement.