In the absence of strong federal regulations to cut greenhouse gases from automobiles, states, including Maine, have passed their own laws. Those efforts were given an important boost recently when a federal judge ruled that state emissions laws are not overruled by federal regulations. To ensure consistency across the nation, Congress should adopt the state rules as the federal standard.

When a dozen states, including Maine, adopted rules to limit carbon dioxide emissions from cars and trucks, automakers sued, saying such rules conflicted with federal fuel economy standards. Further, the carmakers said, the state laws wouldn’t stop global warming and would do great harm to the auto industry.

A federal judge in Vermont disagreed. “History suggests that the ingenuity of the industry, once put into gear, responds admirably to most technological challenges,” Judge William Sessions III wrote.

This was evident at Europe’s largest auto show in Frankfurt, where manufacturers, including Porsche and BMW, touted gas mileage over engine power. American carmakers debuted smaller, more efficient cars than are available here.

In 1993, Maine joined with other New England states in adopting California’s Low Emission Vehicle program, which set stricter standards for vehicle emissions than the federal government. In 2005, the Maine Board of Environmental Protection approved rules that, for the first time, require emissions reductions among all cars on the road, not just small classes of cars. By 2016, tailpipe emissions of greenhouse gases will have to be reduced by 30 percent compared with the 2002 fleet.

To become effective, California still needs a waiver from the U.S. Environmental Protection Agency. An effort in Congress to disallow such a waiver failed last year. However, the federal government has moved slowly in improving fuel economy standards, which is one way to reduce greenhouse gas emissions. If a car goes farther on a gallon of gasoline, it emits less pollution.

Earlier this year, President Bush asked the heads of the Energy, Agriculture and Transportation departments and the Environmental Protection Agency to develop regulations to reduce gasoline consumption by 20 percent over the next decade. He also called for increasing fuel economy standards by 4 percent a year for the next decade.

A month later, the Senate passed an energy bill that would raise average mileage standards from the current 25 miles per gallon to 35 miles per gallon by 2020, which would be the first congressionally mandated increase since 1975. The standards can be lower if federal regulators find the ones set by Congress are not “cost effective.”

This is a start, but the state rules, applied across the country, would achieve larger emissions reductions more quickly.