Colorado will challenge the Trump administration’s expected move Wednesday revoking the ability of states to enact vehicle-emissions standards that are tougher than what is mandated by the federal government.

The Environmental Protection Agency is slated to rescind a waiver granted to California under the Obama administration that allowed the state to create its own emissions rules. The decision has major implications for Colorado and more than 10 other states that have adopted California’s standards.

Colorado Attorney General Phil Weiser said Tuesday night that the Trump administration’s move was an attack on the states’ rights and vowed to take action.

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“This action is a direct assault on our system of cooperative federalism and an effort to undermine the role of states in addressing #climatechange,” the Democrat tweeted. “Colorado will be challenging this ‘unprecedented action.’”

It wasn’t exactly clear what Weiser meant by his plans to “challenge” the decision, thought California Attorney General Xavier Becerra has promised to sue the Trump administration over the move. Colorado could sign onto that legal challenge, which is expected to make its way to the U.S. Supreme Court.

The Trump administration’s revocation has long been expected — as has been the challenge from Weiser and the other states that have adopted California’s emissions rules.

Colorado’s attorney general has also challenged the Trump administration on its rollback of other environmental regulations, like the decisions to end the Obama-era Clean Power Plan and vehicle-emissions standards for manufacturers’ fleets.

If Weiser files or joins a lawsuit challenging the vehicle-emissions decisions, it would mark the 11th legal challenge Weiser has joined or filed against the Trump administration since he took office in January.

MORE: EPA set to end California’s ability to regulate fuel economy, which could impact Colorado

Colorado Gov. Jared Polis made adopting Californoria’s zero-emissions vehicle policy a priority with the hopes that it will force auto dealers to sell more electric vehicles and drive down one of the nation’s leading sources of carbon emissions.

In August, the Air Quality Control Commission voted 8-1 after a three-day hearing to adopt the standards.

The zero-emissions vehicle mandate requires automakers in Colorado to sell more zero-emission vehicles starting in 2023. State officials estimate the change will require automakers to make zero-emissions vehicles 4.9% of the cars sold in Colorado in 2023 and growing to 6.1% by 2030.

Colorado automobile dealers have blasted the rules as forcing people to buy certain vehicles.

The Polis administration on Tuesday fiercely defended the standards in an opinion piece jointly submitted to The Colorado Sun by the chiefs of the state’s public health, energy and transportation departments, as well as the head of the Alliance of Automobile Manufacturers.

“The growing adoption of electric vehicles in Colorado creates a win for the public, the environment, and the quality of life that attracts people to our state,” they wrote.

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