The move by 12 states could coax Congress to pass efficiency limits.
When historians finally take stock, Vermont may look like the mouse that roared – the tiny state that brought the nation's mighty auto industry to heel by requiring cars that emit fewer greenhouse gases.
This is one scenario that could unfold following a federal judge's ruling Wednesday, which upheld a Vermont law patterned after California's mandate that the carbon-dioxide emissions of cars sold in the state must be slashed 30 percent by 2016.
The judge's finding – that federal fuel-economy laws are not in conflict with state emissions laws – is particularly significant, coming on the heels of a US Supreme Court decision in April. That ruling found that the Environmental Protection Agency has the authority to regulate greenhouse-gas emissions, legal experts say.
On the one hand, Wednesday's decision strengthens the hand of states that want to take action against global warming. But in the longer term, the impact from the ruling could lead to one nationwide standard, which is already expected by many.
In addition to the 12 states with California-style laws on the books, another six are close to acting.
The ruling this week could start dominoes falling by:
• Prompting the US EPA to grant California a waiver from the Clean Air Act allowing it, along with Vermont and the 10 other states with identical laws, to begin enforcing greenhouse-gas requirements for cars sold within their borders.
• Causing six additional states – Arizona, Florida, New Mexico, Utah, Illinois, and Minnesota – to proceed with their own similar emissions requirements. Altogether, the 18 states that have such laws – or are leaning toward them – make up about half the US auto market.
• Spurring Congress to reconsider the new fuel-efficiency standards it is currently weighing, which are not as demanding as Vermont's, and mandate a tougher federal requirement that would also reduce greenhouse-gas emissions.