Why does Wüsthof sell a fancy kitchen knife for US$2000, but mass-produce something similar for US$100? Why do some of us mail holiday cards, while sending anything similar by email? Why does the American Journal of International Law print its journal, when interested readers—and there should be many—can read articles like Julian Nyarko's “Giving the Treaty a Purpose: Comparing the Durability of Treaties and Executive Agreements” online? Come to think of it, why bother with Article II treaties, when they too have a near substitute, more easily produced, in congressional-executive agreements? On this last question, Nyarko's article offers an interesting approach and an intriguing finding: if we measure the commitment strength of agreements in terms of duration, treaties are measurably longer and, perhaps, stronger. Having spent several years working on treaty issues for the Restatement (Fourth) of the Foreign Relations Law of the United States, I am acutely (and perhaps embarrassingly) interested in finding out why they matter. In this essay, I note some misgivings about how the article reckons the substitutability of agreements and about treating their age as a proxy for strength—perhaps Methuselah rivaled Samson's might at some point, but that was not how he distinguished himself—before closing by trying to imagine rival inferences that might be consistent with Nyarko's valuable insights.

In “Giving the Treaty a Purpose,” Julian Nyarko distinguishes between treaties and executive agreements and argues that treaties signal a higher level of commitment to our partners in cooperation than do executive agreements because treaties are more durable. Nyarko uses survival-time analysis to demonstrate that treaties last longer than executive agreements—that is, treaties are less likely to drop out of the Treaties in Force (TIF) series in any given year. The longer life of treaties is Nyarko's proxy for their greater durability. Nyarko argues that his result holds “even after controlling for a number of covariates that could influence the durability of the agreement,” like particular presidents, subject areas, and partner countries as well as the degree of divided government. Nonetheless, Nyarko's list omits the most important variable affecting durability as he defines it: intended duration. Sometimes the intended duration of a piece of formal international law is finite. Indeed, as I will explain in this response, under certain (and common) conditions, this choice of a finite duration is what makes the commitment credible (or, in Nyarko's language, reliable).

When I finished reading Julian Nyarko's “Giving the Treaty a Purpose: Comparing the Durability of Treaties and Executive Agreements,” I found my mind wandering through memories of the more than five years I spent working on Capitol Hill as Counsel for the Senate Foreign Relations Committee (SFRC)—a role that often required me to figure out how best to preserve the constitutional prerogatives of Congress in the face of the various types of international agreements the executive branch produced. This essay recounts my impressions of how the Senate handled different agreements in the 2013–2018 timeframe—Article II treaties, the Paris Climate Agreement, and the Iran Nuclear Agreement. Unlike Professor Nyarko's ambitious and impressive work to categorize and statistically analyze the durability of Article II treaties and executive agreements—which I applaud and find useful—this essay is modest in purpose. I contend that how Congress handles different types of agreements is largely a product of specific political dynamics—including political ownership, policy entrepreneurism, and electoral risk—that can be unpredictable. Because of these dynamics, the differences that Nyarko reveals regarding the durability of Article II treaties and executive agreements are unlikely to produce a significant change in official practice.