The Supreme Court will hear arguments today in a case that could bring a lot more rust to a struggling rustbelt. A coalition of 12 states, including Massachusetts, California, and New York, as well as several cities and numerous left-wing environmental organizations, want the high court to order the Environmental Protection Agency to consider regulations on emissions of carbon dioxide.

The regulations in question would officially affect only new automobiles. But the implications of a victory for the plaintiffs would be far broader — indeed, victory would provide the plaintiffs with much of the intellectual and moral ammunition they need to clamp their apocalyptic vision of society on the country as a whole. Automobiles, after all, contribute only a fifth of the carbon dioxide produced by human sources. Next will be power plants, semiconductor factories, and other pillars of prosperity.

The Supreme Court, of course, may decide to uphold a U.S. Court of Appeals ruling that the EPA was within its discretionary rights to reject greenhouse gas regulations, at least for the moment. The appellate court held that the scientific evidence for global warming is still highly speculative. And in a separate opinion, Judge David Sentelle pointed out that the Supreme Court itself has long held that a plaintiff must show actual harm before he can sue for remedies. As the judge wrote, “it is not sufficient that he has merely a general interest common to all members of the public.”

The place for settling matters of common interest, of course, is the political process, not a courtroom or even a regulator’s office. Indeed, the Supreme Court case reflects a deliberate effort to bypass the political process, because global warming enthusiasts haven’t had much success persuading the elected representatives of the people that there is a need for action. Efforts to approve Al Gore’s Kyoto Protocol were turned back in the U.S. Senate by a vote of 95-0.

And for good reason. The global temperature rise in the 20th century has been minimal — and much of it occurred before industrial activity and the automobile were major contributors to greenhouse gases in the atmosphere. The climate actually cooled in the middle part of the century, before heating up again and actually leveling out in recent years. Remember all those “experts” who predicted last year that Katrina was only a warm-up for a devastating hurricane season this year?

If regulators can act on the basis of scientifically speculative threats, based on computer models that are deeply hostage to the assumptions of the modelers, what can’t government do? Global warming is thus the mother of all environmental scares, justifying political intervention in the economy on a scale only a diehard Marxist would have dreamed of.

That’s not an argument for ignoring potential threats to human health and welfare. But insofar as the so-called “precautionary principle” justifies action before all the facts can be known, the same principle argues for a need to be wary of government actions that can — and often do — turn out to be ill-advised, wasteful, and downright dangerous.

Despite inconclusive science, government rushed to ban DDT production in the wake of ecologist Rachel Carson’s famous 1962 diatribe, “Silent Spring,” about chemical threats to the environment. Recently the World Health Organization concluded that had been a severe overreaction that may have cost tens of millions of people around the world their lives because of rampant malaria.

Let’s hope the Supreme Court keeps that holocaust in mind this time around.

Mr. Bray is a columnist based in the Detroit area.