There's a few reasons why this is an important fight. Number one, if they do this, it guts the Clean Air Act to the point where smog in China will look like light fog. Two, it's a punishment for California not being in line with the rest of Trumpville and not deifying our Glorious Leader like the god among politicians he truly is. And three, auto manufacturers really really really wanna make cars that belch black smoke but can't because as California goes, so goes the rest of the nation.
Ironbite-it's ingenious how petty this move really is.