The U.S. Court of Appeals for the District of Columbia Circuit has vacated the Environmental Protection Agency’s rule to delay amendments to its Risk Management Program adopted in the wake of the West, Texas, fertilizer plant disaster.

The EPA under the Trump administration delayed the regulation several times and promulgated a final rule in June 2017 to delay its implementation for 20 months. But in July 2017, a group of 11 state attorneys general sued the EPA for delaying the regulation and the D.C. Circuit ruled in their favor on Friday.

“Because EPA has not engaged in reasoned decision-making, its promulgation of the delay rule is arbitrary and capricious,” the appeals court said in vacating the delay rule.

In May 2018, the agency proposed a rule to rescind the planned changes — a regulation that was seen by some experts as gutting an effort to improve the safety of chemical facilities launched under the Obama administration even as incidents at these facilities continued to occur.

The Obama-era proposal, which features requirements for third-party audits and incident investigations at chemical facilities regulated by the agency, was adopted in the wake of the West fertilizer plant explosion that killed 15 people in 2013. But the EPA said its new proposal related to the Bureau of Alcohol, Tobacco, Firearms, and Explosives’ finding that the incident was caused by arson and not an accidental chemical incident. The fire and explosion at the West Fertilizer Co. killed 12 emergency responders and three civilians and injured more than 300 other people.

The appeals court rejected the Trump administration’s rationale for rescinding the regulation.

“Even were the court to agree for purposes of argument that the cause of the West, Texas, disaster being arson is relevant to some of the accident prevention provisions of the chemical disaster rule, it is irrelevant to the emergency-response and information-sharing provisions, including those that have indisputably been delayed from the original March 14, 2018, effective date,” the court stated. “Given that 12 of the 15 fatalities in the West, Texas, disaster were local volunteer firefighters and other first responders, this would be a fairly weak explanation for delaying provisions that EPA previously determined would help keep first responders safe and informed about emergency-response planning.”

Jordan Barab, former deputy assistant secretary of the U.S. Occupational Safety and Health Administration under the Obama administration, called the appeal court’s decision “a stinging rebuke” to the EPA in his Confined Space safety and health newsletter on Friday.