Two Dozen States, 10 Cities Sue EPA Over Repeal of Climate Change Endangerment Finding

Lawsuit challenges Trump administration's reversal of Obama-era rule that was legal basis for climate regulations.

Mar. 21, 2026 at 1:10am

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Two dozen states, along with more than a dozen cities and counties, sued the Environmental Protection Agency on Thursday, challenging the Trump administration's repeal of a scientific finding that carbon dioxide and other greenhouse gases threaten public health and welfare. The 2009 endangerment finding had been the legal foundation for nearly all climate regulations under the Clean Air Act, but the EPA's recent repeal eliminates emissions standards for cars and trucks and could lead to a broader undoing of climate rules.

Why it matters

The lawsuit seeks to reinstate the endangerment finding, which is crucial for the federal government's ability to regulate greenhouse gas emissions and address climate change. Without this legal basis, the EPA would lose its authority to set emissions standards for vehicles, power plants, and other major pollution sources, undermining efforts to curb global warming.

The details

The lawsuit, filed in the U.S. Court of Appeals for the District of Columbia Circuit, asserts that the EPA's rescission of the endangerment finding abandons its core responsibility to protect public health and the environment. The plaintiffs, which include 24 states, 10 cities, and 5 counties, argue that the Trump administration's repeal ignores the scientific evidence and legal precedent established by the Supreme Court's 2007 ruling in Massachusetts v. EPA.

  • The EPA finalized the repeal of the endangerment finding in February 2026.
  • The lawsuit was filed on March 20, 2026.

The players

Environmental Protection Agency (EPA)

The federal agency responsible for setting and enforcing environmental regulations, including those related to greenhouse gas emissions and climate change.

Letitia James

New York Attorney General, who is leading the lawsuit against the EPA along with attorneys general from Massachusetts, California, and Connecticut.

Joy Campbell

Massachusetts Attorney General, who stated that the state has long been a leader in protecting communities from the dangers of greenhouse gas emissions.

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What they’re saying

“Instead of helping Americans face our new reality, the Trump administration has chosen denial, repealing critical protections that are foundational to the federal government's response to climate change.”

— Letitia James, New York Attorney General

“Climate change is real, and it's already affecting our residents and our economy. When the federal government abandons the law and the science, everyday people suffer the consequences.”

— Joy Campbell, Massachusetts Attorney General

What’s next

The lawsuit is expected to make its way through the court system, potentially reaching the Supreme Court, which has become more conservative since its 2007 ruling in Massachusetts v. EPA.

The takeaway

This lawsuit represents a significant legal challenge to the Trump administration's efforts to roll back climate change regulations, underscoring the ongoing battle between states, cities, and the federal government over the proper response to the threat of global warming.