The Supreme Court appeared divided on Monday over the sole Obama administration program already in place to limit power plant and factory emissions of gases blamed for global warming.

The justices took on a small, complicated piece of the politically charged issue of cutting greenhouse gas emissions in an extended argument that included references to Dunkin’ Donuts stores, football games and light bulbs. The examples were meant to illustrate the vast potential reach of the program, in its critics’ view, or its limited nature, as the administration argued.

The presence of Senate Republican Leader Mitch McConnell of Kentucky in the courtroom underscored the political stakes in President Barack Obama’s high-profile effort to deal with global warming – a policy Obama is pursuing after failing to persuade Congress to enact climate change legislation. McConnell is facing a tough re-election fight in which he refers often to the administration’s assault on the coal industry in Kentucky and elsewhere.

The court’s liberal justices seemed comfortable with the scope of an Environmental Protection Agency permitting program that applies to companies that want to expand facilities or build new ones that would increase overall pollution. Under the program, the companies must evaluate ways to reduce the carbon they release. Carbon dioxide is the chief greenhouse gas.

However, conservative members of the bench indicated they’re skeptical of the EPA’s authority, with Justice Anthony Kennedy as the probable decisive vote. Kennedy seemed most interested in making clear that EPA would retain the ability to combat climate change under earlier high court rulings, regardless of the outcome of this case.

Both sides acknowledged on Monday that the result would not impede EPA’s proposal of first-time national standards for new power plants or its regulations for existing plants expected to be proposed this summer. It will then move on to other large stationary sources such as factories.

The permitting program, though, is the first piece of EPA’s attempt to reduce carbon output from large sources. Justice Samuel Alito suggested that EPA simply rewrote a provision of the Clean Air Act to justify its permitting program and avoid sweeping in tens of thousands of businesses.

“In the entire history of federal regulation what is the best example you can give us of an agency’s doing something like that?” Alito asked Solicitor General Donald Verrilli Jr., defending the program for the administration.

Verrilli sought to explain the EPA’s actions as a way to deal with major sources of pollution, “not to gradually expand the permitting requirement until they’ve got all the Dunkin’ Donuts in America under it. That’s not what’s going on.” About 140 permits have been issued so far, Verrilli said.

But Peter Keisler, representing the American Chemistry Council among two dozen manufacturing and industry groups that want the court to throw out the rule, said that the administration’s description omits an astonishing level of detail discussed by EPA and local permitting authorities, including “whether more efficient light bulbs should be used in a plant’s cafeteria.” EPA decided it wasn’t worth it, Keisler said.

One potentially narrow outcome would preserve the bulk of the program for facilities that already emit other pollutants that EPA regulates.

Verrilli urged the court to leave the permitting program in place. “This is an urgent problem. Every year that passes, the problem gets worse and the problem for future generations gets worse,” he said.

In 2012, a three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit concluded that the EPA was “unambiguously correct” in using existing federal law to address global warming.

Kennedy joined the court’s four liberal justices in the 2007 ruling in Massachusetts v. EPA that said the agency has the authority under the Clean Air Act to limit emissions of greenhouse gases from vehicles.

Two years later, with Obama in office, the EPA concluded that the release of carbon dioxide and other heat-trapping gases endangered human health and welfare. The administration used that finding to extend its regulatory reach beyond automobiles and develop national standards for large stationary sources. Of those, electric power plants are the largest source of emissions.

The utility industry, the U.S. Chamber of Commerce and 13 states led by Texas are asking the court to rule that the EPA overstepped its authority by trying to regulate greenhouse gas emissions through the permitting program.

“Greenhouse gases are not included within the (permitting) program at all,” Keisler said.

In addition to environmental groups, New York, California, Illinois and a dozen other states are supporting the administration, along with the American Thoracic Society, which filed a brief detailing the health costs of climate change.

Chief Justice John Roberts wondered if high school football games could fall under the EPA’s regulation and Justice Stephen Breyer asked if the same would be true at a family gathering of his 500 relatives.

Verrilli’s answer: “Human beings are actually net neutral on carbon emissions, and you will need a chemist to explain that to you. But it doesn’t matter how many family members you have, you won’t get to the limit,” he said.