If you took all the cows in the United States and figured out how much greenhouse gas they emit, would you be able to sue all the farmers who own them?

That interesting legal question came from Justice Antonin Scalia during Supreme Court oral arguments about whether an environmental case against five big U.S. power companies can go forward.

At issue is whether six states can sue the country’s biggest coal-fired electric utilities to make them cut down on the climate-warming carbon dioxide they emit. One lower court said they couldn’t, an appeals court said they could and now the high court will consider where the case will go next. A ruling should come by the end of June.

For now, though, the question was cows.

Attorney Barbara Underwood argued that the five power companies were the largest emitters of carbon dioxide in the United States, making up 10 percent of U.S. emissions. No other company comes close, she said.

Scalia then leaped into the fray.

“You’re lumping them all together,” he said of the five big power companies. “Suppose you lump together all the cows in the country. Would that allow you to sue all those farmers? I mean, don’t you have to do it defendant by defendant? … Cow by cow or at least farm by farm?”

And if you can lump all the cows together and claim they fuel global warming, Scalia reasoned, “you can lump together all the people in the United States who breathe, I suppose?”

Scalia has a point. Both people and cattle exhale carbon dioxide when they breathe, adding to the amount of carbon dioxide in the atmosphere. Environmentalists point to the amount of CO2 emitted by power plants as a more powerful fuel for climate change.

A slightly gamey aspect of bovines is methane, which they emit in copious amounts, and methane is a more potent greenhouse gas than carbon dioxide. But that did not make it into these legal arguments.

Photo credits: REUTERS/Gonzalo Fuentes (A French farmer prepares his cows before the public opening of the 48th Paris International Farm Show in Paris February 18, 2011)

REUTERS/Kevin Lamarque (Justice Antonin Scalia testifies before a House Judiciary Commercial and Administrative Law Subcommittee hearing, Washington, May 20, 2010)