Critical Shifts:
-
Legal and Regulatory Opposition: Colorado Attorney General Phil Weiser testified before the EPA to oppose a Trump administration proposal aimed at rescinding the landmark 2009 endangerment finding, arguing the rollback violates established law and undermines the Clean Air Act.
-
Environmental, Economic, and Health Threats: Weiser highlighted that eliminating vehicle emission standards directly threatens Colorado's physical health, youth mental health, and economy by ignoring scientific evidence and worsening climate impacts like severe droughts and extreme wildfires.
-
Disregard for Scientific and Precedent Foundations: The testimony emphasized that the proposed rule attempts to undo the 2009 finding—which stemmed from the landmark 2007 Massachusetts v. EPA Supreme Court decision—without any grounding in law or science.
___________________________________________________
Colorado Attorney General Phil Weiser testified before the U.S. Environmental Protection Agency in opposition to a Trump administration proposal, issued August 1, 2025, that would negate the EPA’s authority to regulate harmful air pollution from motor vehicles. The proposal would undo a landmark 2009 finding which held that vehicle exhaust contributes to climate change and endangers public health and welfare.
“The effects of climate change in Colorado are impossible to ignore, whether it’s increased drought or extreme wildfire danger, and we know it’s being driven largely by pollution from cars and other sources,” said Attorney General Phil Weiser. “Ignoring common sense, including scientific research from our own government, is a recipe for disaster. Eliminating requirements like vehicle emissions standards and refusing to acknowledge the reality of what is causing climate change puts at risk not only our physical health, but the health of Colorado’s economy. Climate change also exerts a disproportionate mental health burden on young people, in addition to its environmental impacts. The Trump administration is moving to undo the progress we’ve made and I’m going to keep doing everything in my power to stop it from doing so.”
The 2009 endangerment finding was the direct result of the landmark 2007 Supreme Court decision in Massachusetts v. EPA (PDF), which confirmed the EPA’s authority under the Clean Air Act to regulate greenhouse gas emissions that threaten public health and welfare. After years of scientific review, the EPA determined in 2009 that greenhouse gas emissions from motor vehicles contribute to air pollution that harms public health and welfare in numerous ways. The EPA’s new proposal seeks to reverse that finding with no grounding in law or science.
In his testimony, Attorney General Weiser told the EPA that the proposed rollback is contrary to established law, ignores decades of scientific evidence compiled by the agency under multiple presidential administrations, undermines the Clean Air Act’s model of cooperative federalism, and threatens to harm Colorado’s environment and economy.
