The Donald Trump Administration has proposed to revoke California’s long-standing authority to set its own vehicle emission standards. The success of California in mitigating air pollution and reducing greenhouse gas (GHG) emissions under CAA §209—and that of the 15 states that have invoked waivers under §177—is now in question. The Trump Administration argues that the §209 waiver was not intended to “solve climate change” and that its new standards would save consumers $500 billion. Critics have decried this as a lost opportunity to make significant progress on reducing GHG emissions; they also point out that it contradicts the Administration’s stated preference to allow states flexibility to accomplish environmental goals. On December 6, 2018, ELI hosted a Breaking News webinar to discuss the implications of this proposal. As panelists looked forward, they also looked back to the establishment of standards regulating tailpipe pollution in California, an exception that if altered will have significant implications for the future of climate and environmental law nationwide. This Article presents a transcript of the discussion, which has been edited for style, clarity, and space considerations.