Siding with Attorney General Steve Bullock, justices wrote in their order that the case raised too many questions about Montana's contribution to a global problem.

"The court is ill-equipped to resolve the factual assertions presented by the petitioners," justices wrote.

The plaintiffs had attempted to cast the case as solely a legal matter, with the state bound and willing to put in emission limits but unable to do so because of resistance from the Legislature.

Justices also rejected the plaintiffs' claim that the matter was too urgent to wait for action by a lower court that could then be subject to a lengthy appeal.

The petition filed in May was part of a new legal strategy by activists trying to force government intervention on climate change. They want the atmosphere designated as a public trust deserving special protection. Similar lawsuits and regulatory petitions were filed last month by attorneys representing youths nationwide.

Advocates involved in the legal actions have said a victory in even one or two cases would give environmentalists leverage, leading to new regulations to rein in greenhouse gas emissions that scientists say are driving global temperatures higher.

Environmental law experts have described the legal ploy as novel but having little chance of succeeding.

The Montana suit was filed on behalf by a group of trial attorneys representing youths, including some in Missoula. Attorney Amy Eddy of Kalispell said the group was considering its next steps.

"It is clear the Supreme Court simply wanted to avoid deciding this issue at all costs," Eddy said in an email. "Unfortunately, this exposes the state to protracted and costly litigation, which the court will have to rule on anyway at the end of the day."

Attorney General Bullock, a Democrat who is considering a run for governor in 2012, last month asked the court to reject the petition after justices invited the state to respond. Bullock spokesman Kevin O'Brien declined to comment Wednesday.

In his office's response to the petition, Bullock had said the plaintiff's issues would be more effectively addressed through legislative action, litigation in lower courts, or the rule-making process of regulatory agencies.

A group of conservative Montana legislators and other elected officials had sought to intervene in opposition, claiming a ruling that established an atmospheric trust would sidestep the legislature's role in crafting public policy.

Krayton Kerns, a state representative from Laurel and global warming skeptic who helped coordinate the effort to intervene, said he was relieved with the Supreme Court's decision.

But he said he expected the issue to resurface soon.

"This is just another loss for their side, and they have all the time and money on their side and they'll continue to fight this," he said.

The motion to intervene was based in part on Kern and others saying they did not trust Bullock, who campaigned on a promise to protect the state's natural heritage.

"Perhaps the rattling of the swords left him little option but to take such a defense. Obviously, it was entirely adequate," Kerns said Wednesday.