[Ben Ficklin]

California was the only state to impose enviro regs(air quality) before the feds, which means, that only CA is allowed to set regulations more stringent than the feds.

Governor Reagan was the first gov to impose enviro regs on autos.

[Amendment10]

"... California was the only state to impose enviro regs(air quality) before the feds [emphasis added], ..."

FR: Never Accept the Premise of Your Opponent’s Argument

As mentioned elsewhere, the states have never delegated to the feds, expressly via the Constitution, the specific power to regulate intrastate environmental issues.

Also, Reagan had the 10th Amendment-protected power to officially address environmental issues with his state.