can “define and punish” offenses against the
law of nations. Read literally, that seems not to give the
law of nations any place other than as Congress enacts. But founding-era Americans had a robust idea of the
law of nations, so an abstract intent-oriented
approach might instead think their Constitution embraced international
law quite broadly. The historical text-based
approach yields an intermediate position. The
law of nations’ central place in founding-era thought suggests that it came within some of the Constitution’s general phrases. For example, Article III’s “judicial power” likely...