In the early years of the United States, the relationship between international law and statutory interpretation was relatively straightforward. The Supreme Court simply applied the Charming Betsy canon “that an act of Congress ought never to be construed to violate the law of nations if any other possible construction remains.” The presumption against extraterritoriality grew from the marriage of this canon to an international law rule that jurisdiction was territorial. During the twentieth century, the presumption against extraterritoriality separated from the Charming Betsy canon and came to rest on different justifications – first on comity and then on “the assumption that Congress is primarily concerned with domestic conditions.” But these canons remained relatively stable. Near the century's end, Justice Antonin Scalia would list just two principles of interpretation relevant to determining the extraterritorial reach of a statute: the presumption against extraterritoriality and the Charming Betsy canon.

The first decade of the twenty-first century, by contrast, has been one of ferment. In Empagran, Justice Stephen Breyer announced a new rule: construing statutes “to avoid unreasonable interference with the sovereign authority of other nations.” Although he cited the Charming Betsy in support of this rule, avoiding interference with the sovereign authority of other nations is something quite different from avoiding violations of international law. A year later, Justice Breyer (again speaking for the Court) announced yet another new canon in Small v. United States.