Interpreting the commitment and implementing legislation as synonymous doesn’t establish precedent for non-self-execution. Separating treaty commitment from compliance is critical.

But this may not be the best interpretation of these decisions. In other treaty interpretation cases during this period, particularly ones concerning the Hague Convention, the Court actually seems to be embracing international standards of treaty interpretation like those in the Vienna Convention on the Law of Treaties.104 The better reading of opinions like BG Group and Bond, I would suggest, is that the Court is increasingly separating interpretation of the treaty from interpretation of domestic obligations and, in particular, treaty interpretation from interpretation of the implementing legislation.105 And cases that some might suggest should turn on interpretation of a treaty are instead turning on something else.

Thus in Bond, Chief Justice Roberts distinguishes between the Chemical Weapons Convention and the implementing legislation, the Chemical Weapons Convention Implementation Act, even though the language of the two is almost identical. 106 He then focuses on the latter, which, as an act of Congress, is subject to ordinary methods of statutory interpretation, including application of various presumptions. In this case, the Chief Justice applies a presumption that Congress intends to keep the normal balance of federal-state relations unless it clearly states otherwise,107 finds ambiguity in the term “chemical weapons,”108 and thus determines the statute should not be understood to cover Carol Anne Bond’s “ordinary” attempted poisoning—a matter usually left to state law.109 Although Chief Justice Roberts might be inclined to interpret the Chemical Weapons Convention similarly,110 the logic is applicable only to a congressionally-enacted statute.

In BG Group, Justice Breyer uses “ordinary contract”111 principles to determine whether the U.K.-Argentina BIT’s local litigation requirement is a question of “arbitrability” (subject to judicial review) or procedure (left to the arbitrators).112 This might seem odd. Why should a treaty between two non-U.S. parties be interpreted according to U.S. contract law rather than international treaty law? Buried in the opinion is Justice Breyer’s answer. When parties appear before U.S. courts to have awards confirmed or vacated under international arbitration agreements, that process is governed by an American statute, the Federal Arbitration Act, 113 and under that Act, the federal court “should normally apply the presumptions supplied by American law.”114 It is thus in that unique posture that the Court interprets the U.K.-Argentina BIT.

Gonzales v. O Centro Espirita Beneficente Uniao do Vegetal also turns on questions of statutory, rather than treaty, law.115 The Court in that case accepts the executive branch’s view that hoasca is covered by the Convention on Psychotropic Substances.116 Following principles of U.S. law, however, the Court determines that U.S. obligations under that treaty are not, in and of themselves, sufficient justification for denying a religious exception under a U.S. statute, the Religious Freedom Restoration Act.117 Additionally, in Negusie v. Holder, the Court avoids interpreting the Refugee Convention by holding that both the Board of Immigration Appeals and Fifth Circuit incorrectly relied on a prior Supreme Court case.118 The Court thus bases its decision on a domestic source, Supreme Court precedent, over which it can claim ultimate interpretative authority.

This trend of isolating the statutory or constitutional questions from treaty questions runs in parallel with a trend toward less deference to the executive on treaty interpretation. By shifting the question away from areas in which the executive might have special expertise or a special role towards areas within the Court’s ordinary bailiwick, the Court essentially removes the executive from the equation. The executive’s view of a treaty becomes irrelevant.

And Medellín encourages this development. Even if we don’t read Medellín to establish a presumption against treaty selfexecution,119 Medellín does increase the uncertainty of whether any treaty provision will be found to be self-executing.120 This uncertainty increases the importance of implementing legislation or other statutory bases for applying the treaty, which in turn, increases the interpretative focus on those sources rather than the treaty.

In the end, interpreting the Constitution or statutes, rather than treaties, allows the Court to consider questions specific to American law—like federalism or separation of powers—without: (1) doing damage to the treaty; (2) setting precedents about how the treaty should be interpreted by other states; and (3) asserting that the United States is not bound by its obligations. But, the drawback of this trend is that it drives a wedge between treaty commitment and compliance; even enacting the treaty’s precise language into law is no guarantee that the treaty’s obligations will be effective as U.S. law.121