In an executive order signed yesterday, President Donald Trump proposed sweeping changes to the way the country regulates energy production and emissions, including rolling back most major efforts to address climate change instituted under President Barack Obama. In response, 75 U.S. mayors—representing 41 million Americans—have declared their cities won’t enforce Trump’s new policies.

The executive order seeks to halt Obama’s Clean Power Plan, a roadmap to slash U.S. power plant emissions by a third by 2030, and stop the regulation of greenhouse gases which are known to cause climate change.

It also pledges to revive the coal industry (although it is highly unlikely the dying coal industry can be revived), including lifting a moratorium on coal mining on public lands.

The 75 mayors who make up the Mayors National Climate Action Agenda—also known as Climate Mayors—not only issued a strong condemnation of Trump’s actions, they outlined specific ways they will continue their collective work to stop climate change, regardless of the federal government.

The signatories include mayors of all major metropolitan areas like New York City, Los Angeles, San Francisco, and D.C., as well as smaller cities like Santa Monica, California, Park City, Utah, and Eugene, Oregon.

"Nothing can stop us from investing in electric cars and mass transit; from ending our reliance on coal; from installing cool roofs and pavement; or from leading America in solar power,” said Los Angeles Mayor Eric Garcetti, a Climate Mayors co-founder, in a statement.

The Trump administration says its actions will save jobs purportedly lost to the rise of renewable energy. But as these 75 leaders argue, that has not been the case in their cities—in fact, clean energy is driving job growth.

“Climate action is also an investment in our economy and job creation — electric vehicles, solar power, energy efficiency and battery storage are all avenues to restoring our nation’s manufacturing base and create good, middle class jobs,” reads the Climate Mayors letter to Trump. “Today, one in fifty American jobs is now in the solar sector, surpassing employment in oil, gas, and coal extraction combined. Texas is once again experiencing an energy boom — this time, with wind power. In fact, the majority of wind jobs in the U.S. are in congressional districts that voted for you.”

“Nothing can stop us from investing in electric cars and mass transit; from ending our reliance on coal; from installing cool roofs and pavement; or from leading America in solar power.”

Much like the sanctuary city battle playing out between the federal government and cities that have refused to cooperate with federal immigration enforcement, these 75 cities are squaring off against Trump’s new policies with pointed, collective actions that defy the new administration.

When Trump announced he was changing vehicle fuel-efficiency standards, a group of Climate Mayors banded together to order $10 billion worth of electric vehicles for their city fleets to prove that the future of transportation is not fossil fuels.

Although these are powerful statements, these actions could prove risky. This week, Attorney General Jeff Sessions announced that sanctuary cities would be punished by losing federal law enforcement funding.

Cities are already worried about the potential lack of federal funding needed to finance crucial transportation projects—could the same kind of punishment await cities that refuse to enforce the administration’s new outlook on climate change?