For environmental advocates, just about anyone nominated to the Supreme Court would have marked a major improvement from the late Justice Antonin Scalia, who was one of the court's most outspoken critics of federal efforts to regulate clean water, clean air and climate change.

Yet the nomination of Merrick Garland – chief judge of the U.S. Court of Appeals for the D.C. Circuit who was tapped by President Barack Obama on Wednesday – may prove especially welcome news for green groups, the Environmental Protection Agency and the Interior Department.

After nearly 20 years on the bench there, where most challenges to federal regulations like the Clean Power Plan are directed, "Judge Garland is likely more comfortable with broad latitude in agency rule-makings," says attorney Brendan Collins, a partner in the environment and natural resources group at Ballard Spahr, who represents power companies that support the mercury and air toxics rule.