The centerpiece of President Obama’s climate change agenda goes to court on Tuesday, where it will face challenges from 28 states, the coal industry and more than 100 other groups. But in a broad sense, it’s the opening salvo of a fierce legal battle that will decide his legacy on global warming.

Oral arguments in the D.C. Circuit Court of Appeals are the beginning of the legal challenges, not the end, because the case is expected to go on to the Supreme Court, which stayed Obama’s Clean Power Plan in February.