Gov. Mark Dayton said Friday the state will appeal a federal judge's decision striking down part of a landmark renewable energy law and continue fighting any plans by North Dakota utilities to deliver additional coal-fired electricity without offsetting carbon emissions linked to climate change.

U.S. District Judge Susan Richard Nelson said in her ruling Friday that part of Minnesota's 2007 Next Generation Energy Act impacts another state's electricity generation in violation of the Commerce Clause of the U.S. Constitution.

The law, which passed with bipartisan support and was signed by Republican Gov. Tim Pawlenty, says, in part, that utilities may not import additional coal-generated electricity into the state without offsetting emissions.

"While the state of Minnesota's goals in enacting [the law] may have been admirable, Minnesota has projected its legislation into other states and directly regulated commerce therein," Nelson wrote in her 48-page opinion agreeing with North Dakota.

Dayton fired back in a written statement, saying he strongly disagreed with the decision and would "oppose North Dakota's intentions with every means at our disposal. I will defend the State of Minnesota's right to protect the quality of the air our citizens breathe."

Besides the prohibition of imported coal power, the Next Generation Energy Act mandates conservation measures and sets a goal of producing 25 percent of energy used in the state from renewable sources by 2025. Those provisions are unaffected by the judge's decision.

And at least one environmental group contended Friday that the judge's striking down of the provision on importing new coal power will have no practical impact.

"The world is moving on from coal now," said Michael Noble, executive director of the renewable energy advocacy group Fresh Energy. "It's uneconomical, it's impractical. Consumers don't want any more coal."

Noble noted double-digit growth in wind and solar power and said new coal plants aren't needed.

North Dakota Attorney General Wayne Stenehjem, a Republican, disagreed and said state officials there are pleased with the decision.

"We are continuing to look at the prospect of additional generation here because we're living in a nation that needs it. Most of our electricity does come from coal, and that's likely to be the case for a long time to come," he said.