After five years of breath-holding, President Barack Obama finally sounded the death knell for the Keystone XL project last month. In doing so he made clear that "the national interest of the United States would be best served by denying TransCanada a presidential permit for the Keystone XL pipeline."

That perfectly timed announcement a month ahead of the Paris climate summit was seen by many as a "last chance" to reach global consensus on climate policy. The decision has not only provoked the fierce debate you would expect, but has a lot to say about redefinition of the "national interest" of the U.S. in the modern age.

It is not the decision itself that is revealing, but the the language used in White House statements, amounting to a bold statement about America's bid to take a leading role on clean energy globally.

Keystone XL has been a hotly debated policy issue from Day 1. Obama admitted that the drawn-out Keystone saga has occupied an "overinflated role in our political discourse." Other than official evaluations and reviews, the decision was made on the basis of nearly 5 million public comments.

Many will disagree with Obama on his interpretation of the "national interest" — a term that is as slippery as it is emotive, but which has been transformed in recent years by globalization and the emergence of global environmental threats and transnational terrorism. Climate change bows to no nation state.

The official State Department justification outlines a series of findings that led to their decision. Among them are concerns that the project:

  • will have a negligible impact on energy security (thanks, shale boom)
  • will not lead to lower gas prices (as above)
  • raises a range of concerns about the impact on local, communities, water supplies and cultural heritage sites (the Sioux Indians are taking credit for this one)

But all of these considerations are subordinated to one critical factor, namely the recognition that "moving forward with this project would significantly undermine our ability to continue leading the world in combating climate change." In a sharp shift from previous negotiating positions, the White House humbly accepts that the U.S. "cannot ask other nations to make tough choices to address climate change if we are unwilling to make them ourselves."

Even fossil fuel interest groups can swallow commitments to combating climate change through energy efficiency and environmental progress on the demand side. But in Obama's own statement, he crosses bravely into much more contested territory by signalling "we're gonna have to keep some fossil fuels in the ground rather than burn them."

That statement that allies him with the Keep it in the Ground campaign a once-fringe movement, feared by the fossil fuel industry, that is gaining pace and edging into the mainstream. Opponents have already accused Obama of trying to take America back to the Stone Age.

I, like many, stand by the argument that blocking the tar sands supply chain will do little to keep that carbon in the ground. The Canadians will either strike deals with China or turn to the railways to transport their products. But that is not the point Obama is making here this is, above all, a symbolic decision.

Who knows how long the White House has been cooking this one, waiting for the opportune moment to lay down to the gauntlet to Obama's co-negotiators in Paris. It is the follow-up act to the landmark carbons emissions deal Obama struck with China's Xi Jinping almost exactly a year ago.

Tellingly, the State Department's determination on Keystone XL begins by appealing to the national interest in justifying its decision, and ends by calling this "the right decision, for America and the world." As painful as the decision may be for a cluster of interest groups, supporters of the pipeline cling to an outdated and short-term interpretation of the "national interest." This decision has tried to set them straight.