Colorado announced Tuesday it will join a number of states that have moved to implement heightened vehicle emissions standards as the Environmental Protection Agency (EPA) mulls changing laws to weaken federal regulations.

The decision by the state's Gov. John Hickenlooper (D) will add Colorado to a list of 12 states, including California, that have adopted stronger tailpipe emission regulations in an effort to combat climate change.

"Colorado has a choice. This executive order calls for the state to adopt air quality standards that will protect our quality of life in Colorado,” Hickenlooper said in a statement. “Low emissions vehicles are increasingly popular with consumers and are better for our air. Every move we make to safeguard our environment is a move in the right direction.”

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The executive order comes as the EPA is working on a new rule to replace the Obama-era policy that allowed states to set stronger standards, arguing that the current regulations are too stringent and unattainable for car companies.

EPA Administrator Scott Pruitt Edward (Scott) Scott PruittJuan Williams: Swamp creature at the White House Science protections must be enforceable Conspicuous by their absence from the Republican Convention MORE in April announced the agency's plans to change the policy.

"It is very right for us to be here to recognize that what was done in 2011 and 2012, as we evaluate now, is not appropriate going forward and we’re going to get it right," he said at the time at the agency's headquarters.

The EPA has not yet announced its proposed rule, but many expect a draft to be released sometime this summer.

California has led the fight against the EPA's proposed changes to the Obama-era rule, arguing that lowering standards will adversely affect the state's air quality and harm its economy.

California Attorney General Xavier Becerra Xavier BecerraState AGs condemn HUD rule allowing shelters to serve people on basis of biological sex OVERNIGHT ENERGY: Trump casts doubt on climate change science during briefing on wildfires | Biden attacks Trump's climate record amid Western wildfires, lays out his plan | 20 states sue EPA over methane emissions standards rollback 20 states sue EPA over methane emissions standards rollback MORE (D) filed a lawsuit in May along with the attorneys general of 16 other states against the Trump administration over the policy announcement.

"The evidence is irrefutable: today’s clean car standards are achievable, science-based and a boon for hardworking American families. But the EPA and Administrator Scott Pruitt refuse to do their job and enforce these standards,” Becerra said in a statement.