For several years, the federal government has walked a political tightrope as it forestalled efforts to crack down on the greenhouse gases emitted from automobiles.

It has claimed that the U.S. Environmental Protection Agency is powerless to regulate the carbon dioxide that is pumped from tailpipes, because scientists were allegedly uncertain about whether it was a pollutant.

When states, including Washington, took the lead, the feds stepped in and said states could not require that manufacturers produce cleaner-burning autos, because the necessary technology for that would also mean improved fuel economy and only the federal government could regulate that – though you wouldn’t know it from its wimpy efforts to do so.

But the U.S. Supreme Court recently ruled that the EPA can use the Clean Air Act to regulate auto-produced carbon dioxide, which should put an end to the feds’ shaky balancing act. Now the country needs to move forward with strategies that curb pollution and improve mileage.

Barring that, the feds should stop making a federal case out of states’ efforts to pursue solutions. Five states in the West and 10 in the Northeast have been hamstrung by federal attorneys who see clean-car legislation as a usurpation of federal power. Other states are ready to pass such laws or enforce them if the feds lose their case or better yet, drop all litigation.

That means that half the nation’s driving population would soon be able to buy cleaner-running cars that get significantly better mileage. The technology is available to move forward. The Canadian government has already made that demand, and U.S. automakers will oblige.

But American automakers are nervous that such a move would increase the market share of foreign competitors. It’s this same fear that is behind efforts to make sure that tax credits for hybrid vehicles, which are set to expire this year, aren’t renewed.

This strategy of clinging to the past has not served U.S. automakers well. They should realize that they’re in their current financial predicament because competitors did a much better job of looking down the road. It’s long past time that American automakers face the fact that the era of power vehicles sucking seemingly endless supplies of cheap oil is over.

Plus, scientists are increasingly validating the view that humans are part of the global warming problem, and the United States is the world’s biggest contributor.

It would be better if the feds adopted nationwide standards, because motorists in most Midwestern states and the entire South would be left out. But because the automotive industry has sway over the Bush administration and key Democratic members of Congress, that looks to be unlikely.

It would appear that the more realistic scenario for progress is that states adopt and enforce tougher standards, which would force the automotive industry to make the conversion to cleaner cars after it tires of making different models for different states.

That’s a longer route, but at least it would get the nation out of its self-induced rut.