"The U.S. government's authority to regulate air pollution nationwide, often against the wishes of Republican-leaning states, could face new curbs when the U.S. Supreme Court takes on two high-stakes cases in coming months."

"The cases focus on the broad-ranging power wielded by the U.S. Environmental Protection Agency (EPA) under the landmark Clean Air Act, first enacted in 1970.

The law was envisioned as a cooperative effort between the federal government and states in which the EPA sets standards but states have to set plans to comply.

That flexibility has allowed states which favor looser regulations, like Texas and Kansas, to resist - with the support of industry groups like the U.S. Chamber of Commerce and the National Association of Manufacturers - when the agency wants to impose more stringent standards."

Lawrence Hurley and Valerie Volcovici report for Reuters November 24, 2013. [2]