Will the Paris agreement be a legally binding treaty?

Secretary of State John Kerry caused a bit of a stir with comments this week in the Financial Times suggesting that the Paris climate agreement will not be a legally binding treaty.

It appears Mr. Kerry has stepped somewhat inelegantly into a legal morass that doesn’t translate easily into sound bites.

There’s understandably a great deal of confusion about the finer legal points at issue here, in part because the term “treaty” means different things under international and U.S. law. The bottom line is that the Paris agreement will very likely be a treaty under international law, but probably not a treaty as that term is generally understood in the U.S. context.

To elaborate a bit (for a fuller explanation see an excellent legal analysis authored for us by Arizona State University legal scholar Dan Bodansky):

The negotiating mandate that launched the Paris talks back in 2011 calls for an outcome with legal force. That’s generally interpreted by parties, including the United States, as an agreement in a form that constitutes a treaty under the Vienna Convention on the Law of Treaties.

(The Vienna Convention defines a treaty as “an international agreement concluded between States in written form and governed by international law.” It binds only those states that express their consent to be bound—for example, through a process of ratification or acceptance.)

But not all parts of a legally binding agreement have to be legal obligations. The real legal issue in Paris will be whether countries’ individual targets will be binding. The European Union and others say they should. The United States and others say they should not.

The outcome on that question will be an important factor in whether the Paris agreement will require the advice and consent of the U.S. Senate as a “treaty” under Article II of the Constitution.

The United States has joined many agreements over the years through executive action – in other words, by the president acting alone. (These include the Paris Peace Accords ending the Vietnam war and, just last year, the Minamata Convention on Mercury.)

Whether an agreement can be concluded by the president as an “executive agreement” can depend on a mix of factors, including whether it is within the scope of an existing treaty and whether it is consistent with existing U.S. law.

In this case, the Paris agreement will largely elaborate the U.N. Framework Convention on Climate Change (UNFCCC), which President George H.W. Bush ratified in 1992 with the advice and consent of the Senate.

Whether the agreement is consistent with, and can be implemented under, existing law will depend on its contents. A legally binding emissions target (or a new binding financial commitment) would go beyond existing law, so arguably would require approval by the Senate or both houses of Congress.

If the targets aren’t binding, what parts of the agreement will be? Likely, a set of procedural commitments that, for instance, obligate a country to formulate and submit a nationally determined contribution, report on its implementation, and periodically update that contribution.

There’s a legitimate debate over whether making targets binding means they’re more likely to be met, or whether it makes countries less likely to participate or offer ambitious targets. It’s an issue that may not be settled until the final hours in Paris.

What isn’t really in contention, though, is whether the agreement will be a legally binding agreement. It almost certainly will be.