A month after it hobbled the Obama administration’s signature regulation on climate change, the Supreme Court declined Thursday to block a different air-pollution rule that seeks to cut toxic emissions from the nation’s power plants.

Chief Justice John G. Roberts Jr. rejected a request to stay the Mercury and Air Toxic Standards rule, adopted by the Environmental Protection Agency three years ago to tighten restrictions on a class of harmful pollutants that are byproducts of burning coal.

Roberts’s unilateral ruling means the regulation remains in effect while a legal battle continues over whether the EPA properly weighed costs and benefits in drafting the controversial regulation.

More than 20 states have joined a lawsuit opposing the MATS rule, arguing that the pollution controls mandated by the regulation are too expensive relative to the health benefits.

Obama administration officials praised the court’s decision, which gives the White House a much-needed legal victory following last month’s surprise setback to the EPA’s Clean Power Plan. The Supreme Court  on Feb. 9 imposed a temporary freeze on that regulation, which also seeks to impose restrictions on coal-burning power plants with the goal of reducing emissions of greenhouse gases blamed for climate change.

EPA spokeswoman Melissa Harrison said the agency was “very pleased” with Roberts’s decision to let the MATS restrictions remain in effect.

“These practical and achievable standards cut harmful pollution from power plants, saving thousands of lives each year and preventing heart and asthma attacks,” she said. The EPA is expected to complete by late April a new cost accounting that seeks to address the high court’s concerns. The agency contends that the societal benefits from reducing mercury in the environment far outweigh the costs of pollution control equipment that electric utilities will be required to buy.

The states that joined the lawsuit over the regulation had argued for a stay on the grounds that the EPA’s rule is “unlawful and beyond EPA’s statutory authority,” according to a motion filed last month.

Coal-burning power plants are the biggest single source of man-made mercury, a neurotoxin that causes damage to the nervous system, particularly in young children. Decades of mercury pollution from coal-burning has contributed to elevated levels of the toxin in fish.

Environmental groups applauded Roberts’s decision as a win for public health.

“The utility industry has already shown that it is prepared to comply with this vital rule and the EPA has nearly completed the analysis the Supreme Court requested,” said Sanjay Narayan, managing attorney for the environmental law program at the Sierra Club, a nonprofit environmental group. “It would make no sense to suspend these vital protections during the handful of weeks it will take EPA to complete that analysis.”