By Ayesha Rascoe
WASHINGTON (Reuters) - Two U.S. appeals court judges on Friday expressed doubts about the need to throw out a costly U.S. rule on curbing mercury and other toxic emissions from power plants, when the regulator is already reviewing the compliance costs.
The U.S. Court of Appeals for the District of Columbia Circuit heard oral arguments on the Environmental Protection Agency regulation that the Supreme Court ruled in June was issued without proper analysis. It sent the case to the appeals court for review.
Circuit Judges Merrick Garland and Brett Kavanaugh questioned the point of tossing the rule when the EPA had already started updating its analysis.
"Will something really change on the ground if it is vacated?" Kavanaugh asked.
Kavanaugh and Garland are part of the three-judge panel hearing the case filed by industry groups and 21 U.S. states.
Opponents of the rule, which went into effect in April, have estimated it would cost $9.6 billion a year and raise electricity bills.
Kavanaugh noted during the hearing that the EPA has signaled it plans to finish weighing the costs of the rule by April. The agency has said it expects to reach the same general conclusions even with the costs included.
Michigan Solicitor General Aaron Lindstrom, arguing on behalf of the states, said the rule should be thrown out because EPA did not have authority to issue it without evaluating the cost.
The government said the rule applies to about 1,400 electricity-generating units at 600 power plants.
Since many plants have already invested in technology to comply with the regulation, Garland asked how vacating it would help the industry.
"In four months, you may be back under the rule again," Garland said. He said the appellate court often sends rules back to agencies to address deficiencies without actually vacating them.