The Trump administration will propose a plan to freeze emissions standards at 2020 levels while undercutting California's legal waiver to set emissions standards that are stricter than those set by the Environmental Protection Agency (EPA), according to three sources that Bloomberg spoke to.

The news of the Trump administration's plan was leaked in late May , but Bloomberg spoke to people who had seen the plans recently. The proposed rollback of emissions standards is not expected to change substantially.

The Trump administration's EPA has spent the past year and a half laying the groundwork to roll back emissions standards that were finalized by the Obama administration's EPA during President Obama's final month in office, although the rules had been years in the making. Obama's plan would have required automakers to build cars that are increasingly more fuel efficient every few years until 2025.

The Trump administration's plan stays on the Obama-era schedule until 2020, but after that, fuel economy won't continue to get tighter.

In addition, the Trump administration's plan will seek to revoke a waiver that the EPA granted California in the 1970s, which lets the California Air Resource Board (CARB) set its own emissions standards, even if they're stricter than those of the federal government. The waiver was granted at a time when California suffered some of the worst smog problems in the country.

Trump's move could also strip California of powers to set electric vehicle quotas within the state.

However, 16 other states have committed to following California's emissions lead, so it's likely that any attempt to remove California's waiver and replace it with a weaker rule would result in legal challenges from all the states in the union that want a less-polluting vehicle fleet.

Bloomberg reports that the National Highway Transportation Safety Administration (NHTSA), which manages a parallel set of emissions rules for passenger vehicles, would also deny California the right to set its own standards.

"Once the agencies formally unveil the proposal, the public will have a chance to weigh in, with those comments used to develop a final rule that could be implemented as soon as the end of the year," writes Bloomberg.

Update: In a statement to Ars, CARB noted that it could not comment until it saw the final proposal.