President Donald Trump signed an executive order Tuesday instructing the Environmental Protection Agency to begin rolling back the Clean Power Plan, a policy implemented by the Obama administration in an effort to cut carbon emissions and double-down on its commitment to addressing climate change.

The plan has been tied up in litigation since the final version was unveiled in 2015 but was heralded as the Obama administration’s most significant move toward mitigating climate change. The policy was also integral in keeping the U.S. on track to meet its goals as per the Paris Agreement, an international accord detailing specific carbon emission reductions.

Read: How Trump's Clean Power Plan Executive Order Will Affect Climate Change

Trump’s executive order dismantling the Clean Power Plan was met with defiance from an array of different organizations. Politicians, environmental advocates and health officials spoke out against the order Tuesday.

A group of governors and mayors, including California Gov. Jerry Brown, a vocal proponent of climate change regulation, issued a joint statement regarding the order.

“This Order moves our nation in the wrong direction and puts American prosperity at risk. We will assert our own 21st-century leadership and chart a different course,” the statement, signed by the governors of Washington, Oregon and California and the mayors of Seattle, Portland, San Francisco, Oakland and Los Angeles, said. “Climate change is one of our greatest threats, from more wildfires threatening our homes and communities to ocean acidification rocking our shellfish industry to drought hurting our farmers. Too much is at stake – from our health and safety to our jobs and livelihoods – for us to move backwards.”

The group of politicians vowed to continue implementing climate change and environmental legislation on their own, regardless of the administration’s policy decisions.

“Trump is sacrificing our future for fossil fuel profits – and leaving our kids to pay the price,” Rhea Suh, president of the Natural Resources Defense Council, said in a statement. "This would do lasting damage to our environment and public lands, threaten our homes and health, hurt our pocketbooks and slow the clean energy progress that has already generated millions of good paying jobs.”

Environmental groups and politicians weren’t the only ones to weigh in on Trump’s executive order. Harold P. Wimmer, president and CEO of the American Lung Association, issued a statement vowing to fight the administration’s stance on clean air and climate protections.

“Today’s executive order directly contradicts EPA’s core mission of protection public health and the environment, and undercuts the Agency’s ability to achieve the promise of the Clean Air Act – ensuring that all Americans are able to breathe clean, healthy air. Implementing the Clean Power Plan alone would prevent 90,000 asthma attacks and 3,600 premature deaths every year once fully in place,” said Wimmer. “The American Lung Association will actively oppose these regulatory actions at every step of the process, and call on members of the public to do the same. Our families and our health deserve nothing less.”