The high court's ruling undermined Obama administration regulations targeting mercury and other hazardous air pollutants — a different set of regulations from the greenhouse gas limits that Obama is counting on to slow the effects of global warming. Previously, the White House had enjoyed a string of victories defending its environmental rules before the Supreme Court, including decisions allowing the government to regulate pollution that crosses state lines and affirming that the EPA can use the Clean Air Act to reduce greenhouse gases. Another factor: Since the mercury rules had already gone into effect before the Supreme Court ruled against them on Monday, industry groups said the damage had already been done. [...] a move would indefinitely delay Obama's carbon dioxide limits, a key element of his legacy and his biggest selling point as he urged other world leaders to commit their countries to reduce greenhouse gases as part of the climate treaty to be finalized this year in Paris.