(image source: Wikimedia Commons)
Under the original understanding of the Constitution, customary international law features in the U.S. legal system as general law. It is not law of the United States within the meaning of Articles III or VI of the Constitution, and so does not serve as a basis for federal question jurisdiction or override contrary state law. Under the original understanding, the Constitution does not confer the protections of the international law of state-state relations on either foreign states or governments that have been recognized as such by federal political actors. Congress may confer those protections by statute, but in the absence of statute or treaty, they rest on general law. The Constitution’s text indicates that the laws of the United States referred to in Articles III and VI consist entirely of federal statutes. The Federal Convention’s drafting process indicates that members of the convention had that understanding of the text they produced. That process also indicates that the drafters probably understood the laws referred to by the Take Care Clause of Article II to consist of federal statutes. Prominent figures in the ratification debates treated Articles III and VI as using the term “laws of the United States” to refer to statutes. The First Congress drafted the Judiciary Act of 1789 on the assumption that the laws of the United States referred to in Articles III and VI were federal statutes. During the 1793 prosecution of Gideon Henfield for non-statutory criminal violations of the United States’ neutrality, a number of leading figures took the position that the federal courts could entertain prosecutions under unwritten law. It is unlikely, however, that any of them meant to assert that the law of nations was law of the United States within the meaning of Articles III or VI.Fulltext on SSRN.
(source: Legal History Blog)