A group of 23 U.S. states led by California, the District of Columbia and some major cities are challenging a Trump administration decision to weaken Obama administration fuel efficiency standards.
In March, the Trump administration issued final rules requiring 1.5% annual increases in efficiency through 2026 - far weaker than the 5% increases in the discarded Obama-era rules - but abandoned its August 2018 proposal to freeze requirements at 2020 levels through 2026.
Last week, a trade group representing General Motors Co , Fiat Chrysler Automobiles, Toyota Motor Corp and others sided with the Trump administration on its plan and opposed a legal challenge to further weaken the requirements. Other automakers including Ford Motor Co are not backing the administration plan.
California Attorney General Xavier Becerra said the revised requirements "will increase costs to consumers and allow the emission of dangerous pollutants that directly threaten the health of our communities."