New York Attorney General Letitia James is leading a coalition of six states and New York City in a lawsuit against the U.S. Environmental Protection Agency for allegedly failing to regulate interstate smog pollution, her office announced on Thursday.

The lawsuit, filed in the U.S. Court of Appeals for the District of Columbia Circuit, challenged a rule created last year by the EPA that allows states whose smog travels into New York to take no further action to cut down on that pollution.

It has hinged on the so-called good neighbor provision of the Clean Air Act, which requires the EPA to intervene when regulations promulgated by a state are not sufficient to ensure that federal smog health standards can be met in other states where its pollution travels.

The agency determined in 2015 that the planned actions of 24 states would not sufficiently and collectively reduce pollution emissions enough for those standards to be met in New York. Many of those states were directly upwind of New York, including Illinois, Pennsylvania, Virginia, and others.

The EPA did not step in to create a plan for smog reduction that would benefit New York as the Clean Air Act prescribes, according to James. Instead, the agency promulgated a so-called close-out rule that said those states did not have to reduce their emissions any more than already planned to comply with the good neighbor provision of the law.

The two-page lawsuit filed by James on Thursday seeks to strike down the close-out rule as “unlawful, arbitrary and capricious,” according to documents. If the court sides with James, the rule would be vacated and the EPA would have to intervene to develop additional regulations to curb emissions in the states identified in 2015.

“Over two-thirds of New Yorkers regularly breathe unhealthy air due to smog pollution,” James said. “Yet, Trump's EPA is ignoring the Clean Air Act and refuses to require reductions in the pollution largely responsible for this serious public health risk. My office will stand firm for the quality of air in our state by forcing Trump's EPA to follow the law and to ensure New Yorkers' legal right to clean air.”

A spokeswoman for the EPA said the agency does not comment on pending litigation.

The lawsuit builds on previous litigation brought by James and the Connecticut Attorney General's Office that originally challenged the EPA's alleged failure to intervene in the planned emission reduction plans of the states identified in 2015. The decision, handed down in the Southern District of New York, ordered the EPA to address emission levels in states whose pollution traveled into New York.

It's the second lawsuit James has filed against the Trump administration since taking office at the beginning of January. The first sought to allow the commercial fishing industry to net a higher share of summer flounder since, according to the lawsuit, that type of fish has become more populous in New York waters in recent years. That litigation is ongoing.

The attorneys general of Connecticut, Delaware, Maryland, Massachusetts, and New Jersey signed onto the lawsuit filed by James on Thursday. The New York City Law Department is also on the lawsuit.

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