The day after Pennsylvania and 14 other states sued the Environmental Protection Agency over its plan to delay implementation of new clean air standards, the EPA reversed course and cancelled the delay.

The EPA has issued a statement which it says “replaces” its earlier decision to delay the designation of areas that don’t meet new tougher standards for ozone pollution.

That means those areas will be identified this fall as planned, and state and local authorities will have to come up with plans to make their air cleaner.

Pennsylvania Attorney General Josh Shapiro said he understands that the Trump administration is skeptical of government regulation.

“We want to limit regulation as much as we can. I agree on that front,” Shapiro said. “But we also have a responsibility to keep people safe, to keep people healthy.”

The EPA statement says the agency has questions about the new clean air standards, which it developed under the Obama administration.

The statement says the question of whether the new standard for ozone in the air is “set so low as to implicate natural ‘background’ ozone levels in some parts of the country has repeatedly been raised.”

Shapiro said the data and science are clear, and it’s time to work toward cleaner air.

As for why the EPA announced the delay and then abandoned it so quickly after the suit, Administrator Scott Pruitt said in the statement that “we do not believe in regulation through litigation.”

Shapiro said it’s clear the delay wasn’t justified under the terms of the Clean Air Act.

“We demonstrated that the rule of law matters in this country,” Shapiro said, “and that what the EPA was trying to stop the Clean Air Act from fully going into effect was simply wrong and illegal.”