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Customary International Law in the Early Post-Ratification Era
Michael Ramsey

This post continues my discussion of the originalist aspects of International Law in the U.S. Supreme Court: Continuity and Change (Cambridge Univ. Press 2011), a book I co-edited with David Sloss and William Dodge (brief description here).  In my last post, I described how, in the early post-ratification period, the Court aggressively applied treaties basically in the manner of statutes without employing the broad non-self-execution doctrine found in modern law.  Here I will note some of the book’s suggestions regarding the early Court’s application of customary international law.

Unlike the situation with treaties, it is harder to draw firm conclusions from early practice regarding the constitutional status of customary international law.  Two points seem fairly clear (and consistent with other founding era evidence); others seem debatable at best.

First, the Court from its earliest cases in the 1790s used customary international law as a rule of decision in cases in which it had jurisdiction from another source – principally in admiralty and maritime cases.  Glass v. The Sloop Betsey (1794) and Talbot v. Jansen (1795) are key cases launching this practice.  Contrary to the implications of Sosa v. Alvarez-Machain (2004), the Court did not seem to think it needed action by the political branches to authorize the incorporation of customary international law into U.S. law for this purpose.  The Court did not explain the source of its authority to apply customary international law, though elsewhere I have suggested that it naturally flowed from Article III’s grant of “judicial Power”: European and especially English courts routinely used customary international law to decide cases – particularly admiralty cases – prior to the Constitution’s adoption. 

Outside of admiralty and maritime cases, direct application of customary international law proceeded cautiously.  The Court gradually extended its use of customary international law from its core maritime subjects to broader private law areas such as commercial law and conflicts of law, where it became understood as part of the “general common law” recognized in Swift v. Tyson (1842).  Generally this was not controversial, except it was highly controversial whether customary international law could support criminal prosecutions – a question the Court ultimately decided in the negative, along with its general rejection of the common law of crimes, in the nineteenth century’s second decade.

Second, the Court apparently thought that Congress could override customary international law if it did so expressly. That’s the implication of the rule, stated in the 1803 case Murray v. Schooner Charming Betsy, that “an act of Congress ought never to be construed to violate the law of nations if any other possible construction remains”  (at p. 118).  The Court made the point more directly in a series of later decisions beginning with its War of 1812 cases (although some dispute remains: see the insightful set of comments to this post at Opinio Juris).  Again the Court did not explain the source of its belief, although it’s consistent with the text of Article VI, which identifies statutes but not customary international law as part of the “supreme Law of the Land.”

Beyond these points, though, early Court practice does not say much definitive on other controversial constitutional aspects of customary international law.  (1) The early Court did not clearly confront the question whether state statutes (like federal statutes) could override customary international law.  My own view is that several Justices in Ware v. Hylton (1796), which addressed customary international law as well as its better-known treaty holding, thought state statutes overrode customary international law (and again, this would be consistent with the omission of customary international law from Article VI); but my co-editors did not agree, and Ware is a notoriously difficult case to read.  Otherwise, the issue did not come up directly in the early period.  (2)  The early Court did not directly address whether customary international law was part of the “laws of the United States” sufficient to convey jurisdiction under Article III.  The Court did confront something like this issue in two later cases, in 1828 and 1832, which it resolved in a way that suggested no jurisdiction.  (3) The early Court did not directly confront the question whether the President is constitutionally bound to obey customary international law.  In at least two War of 1812 cases it said so in dicta.  But the question was not actually presented in either case, and the Court did not explain the textual basis of its assumption.  (Presumably the basis would be that international law is part of the “laws” which by Article II, Section 3 the President must “take care” are “faithfully executed”).  Thus on three contentious issues of customary international law’s constitutional status, early Court practice does not add much conclusive insight.

Perhaps the most notable aspect of the early Court’s customary international law practice is that the early Court tended to use customary international law indirectly, through application of what has become known as the “Charming Betsy” canon (after the 1803 case), construing ambiguous statutes not to violate international law.  Direct application cases were not as common as often supposed, and were mostly found in admiralty and maritime disputes, which are arguably their own distinct category.