Hours after being sworn in as the new U.S. Secretary of Transportation, Sean Duffy took aim at the main way the federal government regulates miles per gallon for cars and pickup trucks — also a principal way that it controls air pollution and addresses climate change.

President Donald Trump has signed an executive order promising to eliminate what he incorrectly labels “the electric vehicle mandate” imposed under former President Joe Biden.

The U.S. government’s most ambitious plan ever to slash planet-warming greenhouse gas emissions from passenger vehicles faces skepticism about how realistic it is and whether it goes far enough.