California's new policy restricts future purchases of out-of-state, coal-based power to only those facilities that can prevent pollution from entering the air. Any new coal plant that wishes to sell electricity there must be as clean as the best natural-gas fired plant.

The Wyoming authority may consider a legal challenge to the California rule based on interstate commerce law, officials said.

Wyoming officials have said coal-fired power plants would be the most affordable and most attainable option to secure investment in the proposed Wyoming-to-California Frontier transmission line. Once that investment is made, they say the line could carry power from wind, solar and other renewable resources that California wants.

A spokesman for the Wyoming Conservation Voters Education Fund said the California decision might finally force investors to support zero-emission coal technology.

"The writing is on the wall," said Jason Marsden, executive director of Wyoming Conservation Voters. "Investors should think twice before investing their money on new coal-combustion power plants that can't capture global warming pollutants, since California, the biggest potential electricity customer, is no longer interested in buying dirty, coal-fired power."

Waddington said the California policy could have a silver lining for Wyoming. He said California officials may ultimately conclude that they need to invest funds to work with Wyoming to develop clean-coal technologies.