A month after issuing a stay on the Clean Power Plan, the Supreme Court rejected a challenge to another one of the U.S. Environmental Protection Agency’s (EPA) power plant rules this week.

Many see this as a major victory for the Obama administration and an indication that the Clean Power Plan decision was “highly extraordinary.” Obama administration officials praised the court’s decision and EPA spokeswoman Melissa Harrison said the agency was “very pleased.”

The Mercury and Air Toxic Standards rule, which tightens restrictions on harmful pollutants that are byproducts of burning coal, was challenged by 20 states, which argue that the regulations are too expensive. The EPA will issue an economic analysis of the rule in April, but power plants must begin compliance measures now, thanks to the ruling.

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