This story was originally published by Wired and is reproduced here as part of the Climate Desk collaboration.

In its ongoing jihad against federal regulations, the Trump administration has indicated some interest in targeting the ones that attempt to fight climate change. First in its sights: a funky law that gives the state of California the right to make its own rules on automotive emissions. But because of the way laws and business work, the California exemption is one of the most powerful environmental tools in the world.

So California’s not going down without a fight.