On May 1, 2018, California, joined by 16 states and the District of Columbia, filed a Petition for Review of the U.S. Environmental Protection Agency's ("EPA") April 13, 2018, notice of withdrawal of the Final Determination of the Mid-Term Evaluation of greenhouse gas ("GHG") emission standards for model year 2022–25 light-duty vehicles previously issued under the Obama Administration. California v. U.S. Envtl. Prot. Agency, No. 18-1114 (D.C. Cir.). This case has been consolidated with later-filed petitions for review of the same notice by environmental groups and the National Coalition for Advanced Transportation. Nat'l Coal. for Advanced Transp. v. U.S. Envtl. Prot. Agency, No. 18-1118 (D.C. Cir.); Ctr. for Biological Diversity v. U.S. Envtl. Prot. Agency, No. 18-1139 (D.C. Cir.). The states' and National Coalition for Advanced Transportation's statements of issues are due June 4, 2018. The environmental groups' statement of issues is due June 18, 2018. 

EPA's April 13 notice indicates that key assumptions EPA relied upon for the prior Mid-Term Evaluation "were optimistic or have significantly changed and thus no longer represent realistic assumptions." 83 Fed. Reg. 16077, 16078. EPA now believes that the GHG emission standards present feasibility and practicability challenges for auto manufacturers. California, on the other hand, argues that the standards are science-based and achievable and that auto manufacturers are on track to meet or exceed the standards.

The outcome of this suit has the potential to directly affect what GHG fuel emissions standards the lightduty auto industry must comply with in the next several years. It also foreshadows a fight between California and EPA regarding whether California can continue to set its own GHG emissions standards based on its Clean Air Act waiver, as EPA Administrator Scott Pruitt has indicated that EPA is assessing whether to discontinue this waiver. While the current administration has recently shown some willingness to work with California on emissions standards, there remains uncertainty regarding the fuel emissions standards that may be applicable to the auto industry in the near future.