In December 2015, representatives from 195 countries gathered in a small Parisian suburb for almost two weeks. They met to discharge their nations’ obligations under the United Nations Framework Convention on Climate Change (UNFCCC), an almost-universally ratified 1994 treaty that requires its signatories convene annually to combat climate change. One such conference led to the Kyoto Protocol, which entered into force in 2005. The Protocol set binding greenhouse gas emission targets that were especially demanding on developed nations. Though 193 nations accepted the Protocol, its emission target provision expired in 2012. The Protocol’s signatories agreed to extend it to 2020, but only thirty-seven countries actually bound themselves to continued emission targets. Moreover, China and India were exempted from the treaty, and several major emitters – like Canada, Japan, and Russia – withdrew. After 2012, the Protocol’s signatories accounted for only fifteen percent of the world’s emissions.
On December 12, the global community reached a new consensus, aptly dubbed the “Paris Agreement.” Unlike its predecessor, the Paris Agreement mandates that its Parties set their own emission targets and articulate ways to reach them. These “nationally determined contributions” (NDC) will begin in 2018 and nations must update them every five years. The Agreement also imposes reporting and transparency requirements. One provision, likely its most ambitious, limits global warming to two degrees Celsius above pre-industrial temperatures by the end of the century. The last two commitments will be binding obligations, while the NDC requirement is written in non-binding language.
World leaders have hailed the Agreement as a transformative shift toward environmental sustainability. President Obama claimed it was a “turning point for the world” that “represents the best chance we have to save the one planet we’ve got”, and UK Prime Minister David Cameron declared the Agreement was a “vital step[ ] . . . in securing the future of our planet”. UN Secretary General Ban Ki Moon pronounced the Agreement a “historic” and “defining moment on a long journey.”
But will the Agreement become binding international law? Like the Kyoto Protocol, the Paris Agreement becomes binding only if ratified, adopted, or acceded to by fifty-five nations that, together, constitute fifty-five percent of global emissions. A formal signing period is set to begin in New York on April 22, 2016. Given the support from major emitters like China, India, and the United States, there is ample reason to expect the Agreement to garner enough acceptance to enter into force.
A greater issue is whether the treaty will remain binding. The Kyoto Protocol shows just how fickle international climate change politics can be. Despite overflowing support for the initial Protocol – accepted by virtually everyone except the United States – less than one-fifth of its original signatories remained bound to its emission targets when the Protocol expired only seven years later.
The Paris Agreement, like its predecessor, is vulnerable to the same tides of global politics. The lengthy negotiations leading up to the Agreement reveal it was a delicate series of compromises. Perhaps most important was the one between the world’s greatest polluters. Secretary of State John Kerry noted that one of, if not the, driving force behind the deal was China’s willingness to “build a working partnership” with the United States. One can infer that a mutual understanding between these powers paved the way for the Agreement’s success.
Yet two potential obstacles make America’s commitment to the deal tenuous. First, pursuant to Article I of the Constitution, the United States may ratify a treaty only with approval by two-thirds of the Senate, a house currently controlled by Republicans. Given many Congressional Republicans’ lukewarm attitude toward man-made climate change, the constitutional treaty-making process is almost certainly a dead end. President Obama must (and, according to Special Envoy for Climate Change, Todd Stern, plans to) circumvent the Senate altogether. The President can act unilaterally by adopting either a “treaty-executive agreement” or a “presidential-executive agreement.” Treaty executive agreements are authorized by previous Senate-ratified treaties – in this case, the UNFCCC. Presidential executive agreements, on the other hand, arise from a sphere of sole executive power historically carved out from the Constitution’s regular treaty-making procedure. The dearth of case law about either type of agreement leaves unclear whether sole executive action would be legal. Especially with a Supreme Court generally viewed as conservative, President Obama’s attempt to avoid Senate interference may be held impermissible.
Another problem exists even if the Court deems lawful President Obama’s exercise of sole executive power. Unlike with a treaty, experts say President Obama’s successor – who will take office only nine months after the Agreement opens for signature – can unilaterally revoke executive agreements. As of this writing, early signs suggest the 2016 presidential election will be a close one, and the leading Republican candidates share their Senatorial counterparts’ skepticism toward man-made global warming. A Republican Presidential victory, therefore, will likely spell death for America’s participation in the Agreement.
What would American defection do to the Agreement? Countries like China – who reportedly fought during negotiations to lower the Agreement’s obligations and whose acceptance may have been influenced strongly by “partnership” with the United States – may follow suit. Without commitments by the United States and China, support for the Paris Agreement would resemble the Kyoto Protocol, which deteriorated in short order. Of course, the Agreement differs from the Protocol in major ways, especially by granting developed nations the flexibility to fix their own standards. Perhaps that would be enough to keep major polluters like China and India in the Agreement despite American withdrawal. But American defection would greatly undermine the Agreement’s universal quality and likely would reduce other countries’ incentives to fulfill their obligations – especially among nations who view the United States as an economic or political competitor.
 Preeminent international law professor Louis Henkin notes the extent of such powers are “difficult to determine and to state” due to a scarcity of judicial decisions. Louis Henkin, Foreign Affairs and the Constitution, 222 (1996).