There is broad acceptance that the new international climate pact due this December in Paris will be a legal agreement. But governments have yet to agree on precisely which elements will be legally binding, an issue that directly affects whether and how the United States and other key countries will become parties.

The Paris negotiations are taking place under the United Nations Framework Convention on Climate Change (UNFCCC). The outcome will likely be a package containing a mix of legal and political outcomes housed in a variety of instruments: the core agreement, related decisions of the Conference of the Parties (COP), and parties’ intended nationally determined contributions (INDCs).

Under the 2011 Durban Platform for Enhanced Action, which launched the negotiations, the Paris conference, known as COP 21, is to produce a “protocol, another legal instrument or an agreed outcome with legal force under the Convention applicable to all parties.”

In a recent C2ES policy brief, two prominent international legal scholars, Dan Bodansky of the University of Arizona and Lavanya Rajamani of the Center for Policy Research in Delhi, conclude that the Durban mandate arguably requires a treaty within the meaning of the Vienna Convention on the Law of Treaties.  They also note that what the agreement is called – protocol, accord, etc. – is legally irrelevant, and that a legal agreement can contain both binding and non-binding provisions.

Precisely which provisions should be binding was a major topic of discussion in C2ES’s Toward 2015 Dialogue, which brought together senior negotiators from 24 countries to examine options for a Paris agreement.

The final report from the dialogue co-chairs says the agreement should include binding procedural commitments for parties to: inscribe and maintain nationally determined contributions (NDCs), report on progress in implementing their NDCs, and participate in procedures holding them accountable.

There remain sharp differences, however, over whether parties should be legally obligated to implement or achieve their NDCs.  Some believe this would provide greater confidence that the targets will be met, while others believe other parties would lower their ambition if held to a legally binding target, or be unable to accept the Paris agreement altogether. The co-chairs’ report notes that the strength of the agreement will rest ultimately on the transparency and accountability it provides and on parties’ political will to implement it.

Whether NDCs are binding will be one important factor in determining whether and how the United States joins the Paris agreement.

In contrast to countries which provide only a single procedure for entering into international agreements, U.S. law and practice recognizes several routes:

• the best known, involving the advice and consent by two-thirds of the Senate pursuant to Article II of the Constitution;
• requiring approval by both houses of Congress;
• or by the president acting alone on his statutory, treaty, or constitutional authority.

According to a C2ES legal analysis by Dan Bodansky, the president would be on relatively firm legal ground accepting a new climate agreement with legal force to the extent it is procedurally oriented, could be implemented on the basis of existing law, and is aimed at implementing or elaborating the UNFCCC.  On the other hand, if the new agreement establishes legally binding emissions limits, this would weigh in favor of seeking Senate or congressional approval.

With only one more negotiating session between now and December, parties are pressed for time, and the legal issues may be among the toughest to resolve.

In the end, we need an agreement that delivers both broad participation and strong ambition. This will likely require a finessed approach that provides enough legal rigor to ensure a degree of accountability but not so much that key countries choose not to join.