California and 23 other states filed suit against the Trump administration's plan to revoke the state's authority to set stricter tailpipe emissions rules than the rest of the country.
Why it matters: The outcome could have myriad effects, from which vehicles Americans drive years from now to the balance between state and federal power, the Washington Post notes. Automakers, some of which sided with California's stricter emissions targets, are dreading a drawn-out legal battle and being left not knowing which standards to follow.