In 2007, the Supreme Court ruled that if the Environmental Protection Agency (EPA) determined that carbon dioxide emissions threaten public health, the EPA would be required to regulate them. In 2009, the EPA completed its assessment, determining that, yes, carbon pollution endangers public health by changing the climate.

This conclusion is known as the endangerment finding, and it’s the legal bedrock of federal climate protections. It’s also the white whale of climate change deniers.

While conservative think tanks have called for the finding to be overturned, it would be difficult to defeat in court given the mountain of evidence showing carbon pollution is worsening climate change, imperiling public health. A paper published in Science last week shows that in the decade since the initial finding, the evidence supporting the endangerment finding has only mounted. Not only has the science solidified around issues of public health and sea-level rise, but this new report notes that climate change also threatens the public by spurring violence, fueling political instability and hampering economic growth.

This is perhaps one reason why the Trump administration has refrained from mounting a full-scale assault on the endangerment finding and is instead merely looking to limit its scope. For example, a recent proposal to weaken Obama-era limits on carbon pollution from new power plants includes an important footnote calling for public comment on the “correctness of the EPA’s interpretations” of the endangerment finding. The footnote suggests two ways the EPA might reinterpret the finding that would make it difficult to enact new limits on greenhouse gas pollution.

First, it questions whether the agency should have to issue a separate endangerment finding for each specific source of pollution, such as power plants, pipelines and drilling sites. Under President Obama, the EPA considered this issue and decided that as long as a sector was already listed as a polluter under the Clean Air Act, it could be regulated. This is historically how the EPA has interpreted the law. If this interpretation were to change, it would mean that the EPA would have to issue a new endangerment finding for each source of pollution, which would make it more difficult to craft new climate protections.

Second, the footnote questions whether the EPA should regulate carbon dioxide emissions from new coal-fired power plants given that few, if any, are projected to be built. Never mind that any amount of carbon pollution exacerbates climate change. This fact hasn’t stopped political appointees from questioning whether emissions from new plants “contribute significantly to atmospheric CO2 levels.”

EPA air chief Bill Wehrum doubled down on this line of thinking an interview with Bloomberg earlier this month, suggesting there needs to be a threshold that emissions must surpass to be considered a significant contributor to air pollution. In that interview, Wehrum also questioned whether the oil and gas sector emits enough methane to qualify as a significant contribution, which is relevant given that the EPA is attempting to loosen methane regulations on drilling operations. Methane is a shorter-lived but much more potent heat-trapping gas than carbon dioxide.

By reinterpreting the endangerment finding, Trump’s EPA could weaken limits on carbon pollution without having to challenge the mountains of research showing that climate change poses a threat to public health. Thus, while the finding is unlikely to be overturned, vital climate protections are nonetheless at risk as political appointees may still find legal workarounds that let polluters have free rein.

Phil Newell writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture.