Late in the day on Tuesday, February 9, the U.S. Supreme Court stayed, for at least a year and possibly longer, the implementation of the Clean Power Plan (CPP), the US Environmental Protection Agency’s (EPA’s) widely-publicized regulations governing greenhouse gas emissions from existing coal-, oil- and gas-fired power plants. The stay means that the CPP’s requirements and deadlines are on hold, at least until resolution of the pending legal challenges to the CPP. But what are the broader implications of the Court’s decision?

First, the stay decision bodes poorly for the ultimate fate of the CPP, even though the Supreme Court did not opine as to the CPP’s legality. The stay decision signals, at a minimum, that a majority of the Supreme Court is sympathetic to the challengers’ claims that the CPP is unlawful. Indeed, it signals more than that—a distrust of EPA’s assertions about the minimal burdens imposed by the CPP. That said, the CPP may yet survive judicial review and, even if it does not survive, EPA may be able to promulgate a replacement regulation that achieves similar results, although such a replacement would surely take several years to develop.

Second, environmentally, the stay is unlikely to have any immediate effect on emissions levels, primarily because the CPP itself does not require any immediate emissions reductions. But that does not mean the stay has no environmental consequences. The stay fosters uncertainty about the fate of the CPP, and one potential consequence of that uncertainty is that EPA will feel compelled to devote additional resources to reducing greenhouse gas emissions from other sources, especially the oil and gas sector.

The Obama administration has limited time to pursue such alternatives, but the next administration, if it shares President Obama’s commitment to addressing climate change, may focus much more intensively on addressing the carbon content of fuels, to make up for the delays and uncertainties created by the CPP stay decision.

The stay also raises questions about the fate of the recently secured Paris agreement, since some parties to that agreement may now be wondering whether the US is capable of meeting its commitment to reduce domestic greenhouse gas emissions 26 to 28 percent from 2005 levels by 2025. If other countries doubt the reliability of the US commitment, they may be less bold about seeking emissions reductions themselves. Indeed, it is precisely such doubts that may drive EPA to pursue more oil and gas regulations.

Finally, lurking in the Supreme Court’s action may be a deeper signal about the fate of the Chevron doctrine, a topic that should be of interest to all entities subject to regulation in the United States, not just to those subject to the Clean Air Act. A recurring theme in the legal challenges to the CPP is that the CPP raises questions of such extreme economic and political significance that EPA is not entitled to deference as to how those questions should be resolved. It is not clear what role that theme played in the Supreme Court’s stay decision—because the Court’s order does not explain the Court’s reasoning—but it is striking that the Court took the rare and generally unexpected step of staying the implementation of an agency regulation even before any lower court had ruled on the legality of that regulation. If nothing else, the stay decision confirms that the Clean Air Act remains a central, if not the central, battleground in questions over the level of deference that courts owe to administrative agencies.