This is a long and sober article but worth the effort to read. In a nutshell it covers the long and successful history of the regulation of tailpipe emissions and the efforts of the Trump administration to roll them back.
One of the major takeaways from the story is the importance of peer-reviewed, evidence-based work in setting policy. The scientific and economic studies done by Team Trump to justify the rollbacks are junk science and were known to be such two years ago. They are full of very dubious assumptions and horrendous mathematical errors. But still the rollbacks moved forward.
Too bad. For Trump. The political hacks put in charge of policy seem not to understand that changes in government regulations have to be justified objectively and the deeply flawed analyses they based these changes on makes it unlikely that the new tailpipe regulations will survive court challenges.