For those who have followed David Sloss’s work over the years, The Death of Treaty Supremacy is an eagerly anticipated arrival years in the making, and it does not disappoint. One finds in this volume, brought together, strands of his earlier work on judicial deference to executive branch treaty interpretation, the domestication of international human rights law, and “schizophrenic” treaty law. The book also contains David’s trademark close analysis of the treaty interpretation cases of the early Supreme Court. All is presented as part of a broad synthesis.
The book argues that the doctrine of treaty supremacy – the principle that all treaties enjoy a hierarchically superior position to state law – was a “bedrock principle” of U.S. constitutional law for much of U.S. history. As Carmen Gonzalez puts it: “from the earliest days of the Republic until World War II, all treaties ratified by the United States were understood to supersede conflicting state laws pursuant to the treaty supremacy rule.” From that launching point, the book’s main thesis is that the doctrine of treaty supremacy has died a quiet death in the years since World War II. There was no state funeral, just a meandering series of barely audible eulogies. The path from treaty supremacy to the “supremacy of some treaties” was cleared by key developments in international law generally and treaty law in particular: the birth of human rights law, the growth of multilateral treaties, the proliferation of international institutions, and the increasingly broad and deep scope of international law.
Others in this symposium have discussed the book’s value in terms of its historical analysis, constitutional interpretation, and its practical value to human rights litigators. As this on-line symposium draws to a close, it is important to note that the Death of Treaty Supremacy opens up new avenues for research. For example, David Stewart observes that “the story of our Constitution is largely one of judicial adaptation and reinterpretation in light of changed circumstances.” In response to the book’s “problem  with the lack of political transparency” of the process of interring treaty supremacy, Stewart argues that “it is hard to see how a plebiscite or process of formal amendment with respect to the treaty power might actually work.”
David’s observation usefully puts the book’s main claim in perspective. Is The Death of Treaty Supremacy primarily a book about treaty law? About constitutional interpretation? About legal transformation more generally? When we read it a second time, should our frame of reference be Bruce Ackerman’s work on transformations? Or other slow processes of erosion and transformation that have taken place in U.S. treaty law?
If the latter of these, consider treaty interpretation. For approximately a century, it was a bedrock principle of American treaty interpretation that treaties were a kind of contract. The result was that for a long stretch of time, key principles and techniques of the private law of contracts were applied to the interpretation of treaties. Several of the opinions in Ware v. Hylton proceed on this assumption. Ware and its progeny thus established judicial independence in interpreting the nation’s treaties, and did so in part by employing common law contract adjudication as a point of reference. That judicial independence takes the form of the search for mutual intent in bilateral treaties, attention to non-English treaty texts, the emergence via Justice Story of “liberal interpretation,” and notable instances in which the Supreme Court rejected interpretations of treaties that were offered by the U.S. administration in power.
The late 19th century brought the gradual and quiet arrival of a different analogy for treaty interpretation: the treaty as statute. With methods of statutory construction finding their way into the interpretation of the nation’s international agreements came important changes: more deference to the Executive Branch, more reliance on unilateral sources such as U.S. legislative history, less attentiveness to the non-English text of the agreement, less of a willingness of U.S. courts to consider what other states party sought from the treaty, and fewer instances in which foreign claims of breach by the United States were vindicated in U.S. courts. In recent years, other versions of treaty interpretation (e.g., Chevron deference) ask us to go even further from the assumptions held by the Founding generation.
As with the death of treaty supremacy, the prolonged decline of a genuinely applied contract model of treaty interpretation has taken place largely without transparency or clearly articulated justification. Unlike treaty supremacy, the Founder’s assumptions and intentions were not recorded in an express textual provision in the Constitution, though there is abundant evidence that they saw treaties in contractual terms and, of course, they treated some of their assumptions as so natural and obvious as not to require express statement.
So then, if the death of treaty supremacy was a silent and invisible constitutional amendment, can the same be said about the changes in how generations of Americans interpret treaties? And if either one is cause from the perspective of transparency and legitimacy, what about when the two processes occur simultaneously?
For more on the transformation of U.S. treaty interpretation, see the soon-to-be-released co-authored volume, Supreme Law of the Land? Debating the Contemporary Effects of Treaties within the Legal System of the United States, by Cambridge University Press, co-edited by Greg Fox, Brad Roth, and Paul Dubinsky.