The Supreme Court appeared divided as it ventured for the first time today into a raft of legal questions surrounding the regulation of heat-trapping greenhouse gases.

Justices spent most of the time during its one-hour oral arguments examining whether Massachusetts and 11 other states and environmental groups have standing under the Constitution to challenge a U.S. EPA decision not to regulate greenhouse-gas emissions from new cars and trucks.

Jim Milkey, an assistant attorney general for Massachusetts, urged the court to force EPA to reconsider its 2003 ruling not to regulate the gases. Uncontested science shows climate change is causing ocean water expansion and sea-level rise, which Milkey explained is like "lighting a fuse on a bomb" for coastal states.

"The injury doesn't get any more particular than states losing 200 miles of coastline, both sovereign territory and property we actually own, to rising seas," Milkey said.

At least two members of the court -- Chief Justice John Roberts and Justice Antonin Scalia -- signaled they had doubts about Massachusetts' ability to show it has standing in the case.

Roberts, for one, said he had problems with the theory that a Massachusetts victory would start a domino effect of regulation that halts global warming. "That strikes me as sort of spitting out conjecture on conjecture, the sort that we disapproved of," he said.

Scalia began the hearing with a pointed question aimed at discerning the immediacy of global warming's threats. "When?" he asked. "I mean, when, is the predicted cataclysm?"

Milkey replied that EPA could begin regulating greenhouse gases from new cars and trucks, thereby making a relevant dent in world emissions. "It is important to point out that because of the scale of the problem, relatively small percentage deductions in global emissions can lead to real world results," Milkey said.

Justice Kennedy seen as swing vote

Legal analysts predict Justice Anthony Kennedy is poised to be the critical swing vote on standing. During oral arguments, the appointee of former President Reagan hinted that Massachusetts has room to advance its case.

Addressing Gregory Garre, the deputy U.S. solicitor general representing EPA, Kennedy said, "Your problem, I think, you take the position, the proposition that the greater the harm, the greater the risk, the smaller the probability has to be before it is reasonable to act, and necessary to act."

Garre insisted the Supreme Court should not order EPA to re-examine its decision unless Massachusetts can show the regulations would help to offset climate change. "You have to show that granting the relief requested is likely to redress the alleged harms," he said.

Justice Stephen Breyer indicated a new EPA rule could trigger wider action domestically, including sequestration of CO2 emissions from power plants. "Before you know it, they decide any one of 15 things, each of which has an impact, and lo and behold Cape Cod is saved," he said.

Massachusetts successfully convinced the Supreme Court earlier this year to take its case after losing a split 2-1 decision in a lower court.

'It's very close'

Legal experts tracking the case predicted the Supreme Court sits narrowly divided -- though few were willing to pick a winner.

"My best guess is it's not going to be entirely satisfying to anybody," said former EPA air pollution chief Jeff Holmstead, now an industry attorney at Bracewell & Giuliani. "Based on the questions, it's not one of those cases where you get a sense the justices are all seeing it a certain way."

Holmstead added, "I think it could go either way. It's very close."

Speaking at Georgetown University Law School, former EPA general counsel E. Donald Elliot said he expected Massachusetts to squeak by with a narrow victory on standing. Elliot, who served under former President George H.W. Bush, said the current Bush administration may be forced into revisiting the climate issue before it leaves office in January 2009.

Richard Lazarus, faculty director of Georgetown's Supreme Court Institute, went a step further than Elliot in predicting a unanimous Massachusetts victory on the question of whether EPA has the authority under the Clean Air Act to regulate the gases. Given the justices' knowledge of the issues, Lazarus also said he could envision the Supreme Court narrowly deciding that EPA did not exercise ample discretion when it opted against setting new auto standards.

"I think it was a good day for petitioners," Lazarus said. "It's reassuring when you see the justices get it."

Norm Fichthorn, an industry attorney at Hunton & Williams, said the case is important not because of its ties to climate change regulations. "This case is not about all that much," he said. "It's not about global warming. It's an administrative law case."

Asked to handicap the Supreme Court's opinion, Fichthorn said he expects the Democrat-controlled House and Senate will find plenty of room to maneuver in 2007. "However this case is decided," he said, "it is likely to further shift the attention to Congress."

The Supreme Court is expected to issue its opinion by next summer. The case is Massachusetts v. Environmental Protection Agency, 05-1120.

Click here for the oral argument transcript.