The Supreme Court has given California, as well as 11 other states, a green light to implement strict vehicle-emission standards that could lead to more fuel-efficient cars as early as next year.

In a 5-4 ruling, the court, in its first case concerning global climate change, declared that carbon dioxide and other gases considered key culprits of the greenhouse effect are pollutants under the Clean Air Act. That means the Environmental Protection Agency has the authority to regulate those emissions in new cars and trucks.

It had been EPA's long-standing refusal to act on these emissions that brought the agency before the nation's highest court. The EPA had insisted it did not have the authority to regulate those emissions and that, further, the science on global climate change was too uncertain to warrant regulation.

The five justices would have none of it. In the majority opinion, Justice John Paul Stevens wrote: "EPA has offered no reasoned explanation for its refusal to decide whether greenhouse gases cause or contribute to climate change."

The minority, roughly, the four conservative justices, argued that the plaintiffs, a coalition of states and environmental groups, lacked standing and that the issue should rightly be settled by the executive branch and Congress.

Whatever its legal merits and they seem considerable the decision comes at the right time. The political consensus on global climate change has shifted, even within the Bush administration.

The states are moving ahead with or without the federal government because of a special provision in the Clean Air Act that gives California, out of consideration of its extreme pollution, the authority to enact its own air pollution rules, as long as the federal government agrees. Other states can, and have, followed California's lead. Ten have passed similar emission laws and wait for the government to issue them waivers.

In effect, California, with its tenacious will to clean its own air and with the full support of Republican Gov. Arnold Schwarzenegger, has been at the forefront of environmental protection. Its continued unwillingness to shirk what it clearly sees as its duty to protect citizens from harm has now been upheld by the Supreme Court.

The high court's ruling boosts gaining EPA approval of the California's regulations on tailpipe emissions, a law authored by former Assemblywoman Fran Pavley, of Agoura Hills, and passed by the Legislature. Last year, Gov. Schwarzenegger, in endorsing the Democratic-sponsored emissions law, urged President Bush and the EPA to allow the state to implement its law.

Unfortunately, the ruling does not mean immediate implementation of California's emission law. That must wait until a lawsuit brought by the auto industry is resolved. That lawsuit has been held up while the Supreme Court decided the EPA case. With that case settled, the lower court should quickly rule in favor of California based on the Supreme Court's decision.

Automakers had argued that the strict emission standards would, in effect, set fuel-economy standards, something the auto industry says can only be set by the federal government.

The federal government should set tough fuel-economy standards and if California's tough emissions law forces the government to act sooner rather than later, all the better.

Global climate change has been shown to be a looming threat. Efforts to keep any change from spiraling out of control must begin now.

California has set the bar on environmental protection. The Supreme Court has upheld its right to do so. The federal government has been given a mandate to act; it must do so because doing nothing is no longer an option; doing something benefits all.