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The Supreme Court Tuesday night halted implementation of the Obama administration’s Clean Power Plan, which reduces carbon emissions from power plants, until a legal challenge by Republicans, coal companies, and Laurence Tribe is decided in June. (Read Andrew Rice’s 2015 New York Magazine profile of Tribe to understand the legal strategy that won this verdict.) The 5–4 decision, which ran along familiar partisan lines, does not kill the administration’s power plan. More importantly, it also does not stop international action to reduce greenhouse gasses, which was negotiated at December’s international summit in Paris and which has been proceeding at a breakneck pace since. (Investment in green-energy sources has soared.) But it does indicate that the five Republican-appointed justices are giving strong consideration to blocking the administration’s rules.

The chronology of this case dates back to 2007, when the Court ruled that, if the Environmental Protection Agency finds that carbon dioxide creates health hazards, the administration must regulate it as a pollutant under the Clean Air Act. The Bush administration, which was still in office at the time, evaded this ruling by refusing to open emails from the agency’s scientists reporting their findings. The Obama administration has regulated different kinds of carbon emissions, but its regulations on power plants are the most novel form.

What makes the administration’s plan legally vulnerable is not that it goes too far in blocking dirty energy, but that it doesn’t. The Clean Power Plan gives states flexibility to reduce overall power-plant emissions in the most cost-effective way, rather than use a traditional command-and-control approach of banning dirty energy sources (i.e., coal). A straight coal ban would be legally safer, but it would also cause higher energy prices because it would not allow for flexibility in states that have a hard time finding other sources of electric power.

Because the Supreme Court ordered the regulation of carbon in the first place, there’s little doubt that some kind of power plan could be designed that would pass legal muster. The risk is that the clock is ticking on the Obama administration’s term, and if the Court strikes down this plan, and a Republican administration takes office, it will probably decide to let power plants emit all the carbon they want. Which would be bad, and which also illustrates the enormity of the stakes in November. Democrats need to hold on to the White House or literally risk planetary disaster.