The U.S. Environmental Protection Agency announced it will take formal steps to repeal the Clean Power Plan, the Obama administration policy to reduce greenhouse gas emissions from power plants.

“The war on coal is over,” EPA administrator Scott Pruitt said at an event in Kentucky on Monday. “Tomorrow in Washington, D.C., I will be signing a proposed rule to roll back the Clean Power Plan. No better place to make that announcement in than Hazard, Kentucky.”

The Clean Power Plan, created by executive order in 2015, is the key component of the U.S.’s Paris Agreement pledge to combat climate change. President Trump has also promised to pull the country out of the international agreement. A leaked copy of the EPA’s repeal argues that the U.S. would save $33 billion by not complying with the regulation, and that it doesn’t provide significant health benefits, as the Obama administration claimed.

The Clean Power Plan has been caught up in the courts for years due to several lawsuits by conservative states over its legality. Several environmental groups have now pledged to fight this week’s EPA decision in court, further tying up the policy in the judicial system.

Meanwhile, fossil fuel power plants have already begun moving away from coal in recent years, burning less-carbon-intensive natural gas instead. From 2000 to 2008, about 50 percent of U.S. electricity was generated by coal. In 2016, that share was down to 32 percent, with natural gas outstripping it for the first time with 33 percent of electricity generation.

Energy experts say power plants will continue to move away from coal, but that repealing the Clean Power Plan could slow this transition.