Seven national environmental groups are challenging the EPA's decision to freeze fuel economy standards in the year 2022.
The petition to review the decision is part of what is likely a years-long legal battle over the standards, which automakers lobbied to relax when Donald Trump was elected president.
After the election, GM, Ford, and Fiat Chrysler, along with other automakers, asked the EPA to re-open what's known as the midterm review. That is a process to give automakers a chance to show that the strict fuel economy regulations being proposed are not feasible, and should be weakened.
The EPA under the Obama administration decided the standards were feasible; the EPA under the Trump administration decided they were not.
In fact, the EPA is now giving automakers something they do not want. By freezing rather than weakening the standards, the government is now on a collision course with California, which has a waiver allowing it to set its own standards.
California says it has no intention of relaxing the standards, which automakers, the federal government, and California all agreed to in 2010. That could mean automakers would be forced to build two sets of cars to meet two standards, something that would be hugely expensive.
The NRDC says automakers opened up a Pandora's box when they tried to weaken the standards. The group says the best thing for everybody is to abide by the previous decision.
But it is unlikely the Trump administration will do that; instead, the government appears poised to try to wrest California's waiver from it.