The US Supreme Court Tuesday took on six cases related to federal regulation of greenhouse gasses, raising expectations for a much-awaited ruling in the debate over climate change legislation.

The court announced it was combining the six suits from plaintiffs in the chemical industry, the Chamber of Commerce, and the state of Texas, each protesting carbon emissions regulations put in place by the Environmental Protection Agency.

All six cases address just one question: Whether the agency "permissibly determined that its regulation of greenhouse gas emissions from new motor vehicles triggered permitting requirements under the Clean Air Act," the court said in announcing it would take the appeal.

The court refused to consider three other appeals on the same issue.

The nation's highest court also agreed to weigh in on whether a gun owner can legally re-sell his firearm to someone else.

However, as it has in the past, the court refused to hear an appeal on a case regarding the right to own a gun, citing protections under the second amendment.

At issue was a Maryland law that aimed to restrict gun purchases to only those individuals seeking a firearm for "a good and substantial reason."