SALT LAKE CITY — In a major victory for the energy industry, the U.S. Supreme Court on Monday ruled against federal regulators' attempts to curb mercury emissions from power plants, saying the government wrongly failed to take cost into consideration.

The 5-4 decision overturns the landmark rule, which was the first attempt by the U.S. Environmental Protection Agency to curb mercury and other pollutants from coal-fired power plants.

Michigan was joined by 21 other GOP-led states, including Utah, in its fight to get the rule tossed.

One day prior to the rule taking effect, the Carbon power plant west of Price shut its doors, with PacifiCorp deciding the upgrades would be too costly for the '50s-era plant. The plant's geographical configuration, tucked away snugly in a canyon, also precluded expanding the footprint of the facility with the installation of large pollution scrubbers.

Bryce Bird, director of the Utah Division of Air Quality, said the plant had been targeted for closure as part of PacifiCorp's long-term plans, and the rule moved that decision up by a few years.

The Energy Information Administration predicted that 90 percent of the nation's power plants expected to be shut down by 2020 will actually close by 2016 in part because of the rule impacting mercury.

In Monday's ruling, the court pointed out that the EPA refused to consider costs when it crafted its rule, even though its own estimates put the annual costs to power plants at nearly $10 billion a year, while benefits from pollution reductions were pegged at between $4 million and $6 million.

"The agency gave no thought to cost at all, because it considered cost irrelevant to its decision to regulate," and in doing so, strayed far beyond the "bounds" of the Clean Air Act, the court said.

The EPA argued it need only find it "appropriate and necessary" when it decides to regulate power plant emissions and could later factor in cost when it determined how "much" to regulate.

Justice Antonin Scalia said the EPA's reasoning was flawed.

"By EPA's logic, someone could decide whether it is 'appropriate' to buy a Ferrari without thinking about cost because he plans to think about cost later when deciding whether to upgrade the sound system," Scalia wrote.

The court concluded it was unreasonable for the EPA to conclude that cost was irrelevant in its decision to regulate power plants and that the agency must consider cost if it deems a regulation "necessary and appropriate."

American Energy Alliance President Thomas Pyle hailed the ruling.

"Today’s Supreme Court decision is an important step toward reining in the Environmental Protection Agency. For too long EPA has ignored the costs of its regulations, which have become so large that they not only harm the economy, but also the health and welfare of American families," he said.

Clean air advocates were disappointed with the court's decision and urged that strong limits are necessary for pollutants such as mercury, which is a neurotoxin that harms children's developing brains and nervous systems.

"It's very disappointing that the Supreme Court chose to rule today against safeguards designed to protect America's children and families from cancer-causing carcinogens and brain-damaging toxins like mercury, lead and chromium," said Matt Pacenza, executive director of HEAL Utah.

"However, despite today's setback, the march away from dirty and dangerous coal power towards clean energy continues. There’s no turning back the clock on the shift to renewable energy and energy efficiency which Utahns so clearly want."

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