"The Court finds that injecting itself into the global warming thicket at this juncture would require an initial policy determination of the type reserved for the political branches of government," Jenkins wrote in approving the automakers' motion to dismiss the case.

The suit, filed in September, targeted General Motors Corp, Ford Motor Co, Toyota Motor Corp, the US arm of Germany's DaimlerChrysler AG and the North American units of Japan's Honda Motor Co and Nissan Motor Co Ltd.

"The Court is left to make an initial decision as to what is unreasonable in the context of carbon dioxide emissions," Jenkins wrote. "Such an exercise would require the Court to create a quotient or standard in order to quantify any potential damages that flow from Defendants' alleged act of contributing 30 percent of California's carbon dioxide emissions.

"The balancing of those competing interests is the type of initial policy determination to be made by the political branches, and not this Court."

The suit was the first seeking to hold manufacturers liable for global warming damages caused by greenhouse emissions. It said cars made by the six automakers account for more than 30 percent of human-generated carbon dioxide emissions in California, the most populous US state.

"We understand why a district federal judge may not want to jump into a global warming thicket with both feet," Ken Alex, California's supervising deputy attorney general, said in an interview. "Having said that, the basic tenet of law is that where you describe a harm then there needs to be a remedy for it."

"Right now because the political branches -- the federal government, Congress and the executive branch -- have not acted, the state of California is left without a remedy."

Alex said his office would consider whether to appeal the case to the 9th US Circuit Court of Appeals, saying judges frequently decided reasonable standards in cases such as dumping of pollution into rivers.

According to the suit, California spends millions of dollars to deal with a reduced snow pack, beach erosion, ozone pollution and the impact on endangered animals and fish.