A U.S. appeals court on Friday shut down an effort by Trump administration environmental regulators to continue delaying an Obama-era chemical disaster rule, saying the agency was making a “mockery” of federal law and “grasping” at generalized authority to avoid implementing the regulations.

The U.S. Court of Appeals for the D.C. Circuit struck down, unanimously, a “delay rule” the U.S. Environmental Protection Agency adopted last year to freeze enforcement of the Obama administration provisions. The rules, which the EPA put on hold until February 2019, were drafted in response to chemical-plant disasters, including the April 2013 deadly explosion of a fertilizer plant in West, Texas. The regulations would expand safety audits, emergency response coordination and technology requirements.