Environmental-Protection-Agency Photo Credit: Diego M. Radzinschi/ALM

State Attorney General Barbara Underwood announced a multistate lawsuit against the U.S. Environmental Protection Agency on Wednesday for seeking to roll back an Obama-era climate change policy.

Ten other states have also signed onto the lawsuit, which claims the EPA violated the Clean Air Act in April when it issued a guidance on the use of greenhouse gases used commonly in refrigeration and air conditioning.

Those are hydrofluorocarbons, or HFCs, which the Obama administration moved to prohibit or severely limit in 2015. The Obama-era rule was estimated to avoid 26 to 31 million metric tons of greenhouse gases annually by 2020, Underwood’s office said.

Two HFC manufacturers sued the EPA over the 2015 rule, partially claiming victory in 2017.

HFCs are classified as greenhouse gases, but they do not substantially deplete the ozone like other gases, according to NASA. The U.S. Court of Appeals for the District of Columbia ruled that the EPA was allowed to block companies from using HFCs as a new replacement for ozone-depleting substances. But in a split decision, the court said the EPA could not force manufacturers to ditch HFCs if they had already switched to them from another ozone-depleting substance.

The guidance issued by the EPA in April throws out the 2015 limits on HFCs in their entirety, Underwood’s office said. The guidance was issued without a public notice or opportunity for comment, which Underwood said violates the federal Clean Air Act.

“The Trump EPA is seeking to gut critical climate protection rules through the backdoor—once again endangering New Yorkers while thumbing their nose at the law,” Underwood said. “My office will continue to fight back against the Trump administration’s brazen disregard for rule of law, and the health, safety and welfare of New Yorkers.”

The section of the Clean Air Act Underwood referred to allows a court to reverse the decision by the EPA if the agency acts “without observance of procedure required by law.” The lawsuit argues the agency violated that part of the law when the guidance was issued without warning.

The Obama-era rule was ordered based on a part of the Clean Air Act added in 1990 designed to phase out ozone-depleting chemicals. The law requires, according to its text, that any replacement for an ozone-depleting chemical by manufacturers must “reduce overall risks to human health and the environment.”

Allowing HFCs to be reintroduced conflicts with that part of the law because they contribute to climate change, Underwood’s office said. They also believe allowing HFCs would make it harder for New York to reduce climate change pollution. The state has committed to reduce emissions 80 percent by 2050.

Wednesday’s lawsuit is the latest in a string of legal challenges from New York’s attorney general against the EPA since Trump took office in 2017. The office has sued the agency over methane emissions, clean water protections and more.

Attorneys general from California, Delaware, Illinois, Massachusetts, Minnesota, New Jersey, Oregon, Vermont, Washington, Pennsylvania and the District of Columbia joined Underwood in the lawsuit.

An EPA spokesperson said the agency does not comment on pending litigation.