The Constitution's Text and Customary International Law

46 Pages Posted: 30 Nov 2017 Last revised: 14 Apr 2021

See all articles by Michael D. Ramsey

Michael D. Ramsey

University of San Diego School of Law

Date Written: November 19, 2017


The Constitution’s text does not directly address the role of unwritten international law in the U.S. domestic legal system, apart from giving Congress the power to define and punish offenses against the law of nations. This may seem surprising, as the Constitution’s framers were concerned about compliance with international law (then called the law of nations). Modern commentators have advanced various theories of the Constitution’s original relationship to the law of nations, ranging from the view that the Constitution fully incorporated the law of nations as U.S. federal law to the opposite view that the law of nations has no status in U.S. domestic law until incorporated by Congress pursuant to the define-and-punish power.

This essay defends an intermediate position based on the Constitution’s text and historical background. First, it argues that the law of nations was not supreme over state law nor the basis of federal court jurisdiction under the Constitution’s original meaning. In particular, the text’s distinct treatment of treaties – which it expressly makes part of supreme law and the basis of federal jurisdiction – strongly implies a different status for unwritten international law. The Constitution’s framers confronted parallel problems of states violating U.S. treaties and states violating unwritten international law. But in drafting the Constitution they did not provide parallel solutions. This indicates a distinct approach for unwritten international law, requiring action by Congress (or the treaty-makers) to convert it into supreme domestic law. Second, however, this essay argues that the unwritten law of nations could be a rule of decision for U.S. courts with appropriate jurisdiction if it did not conflict with other domestic law. English and American courts prior to the Constitution routinely used the law of nations as a rule of decision, and there is no reason to suppose that the federal courts’ “judicial Power” granted by Article III did not include this traditional authority. Moreover, U.S. courts in the immediate pre-ratification period routinely used the law of nations as a rule of decision without objection. Thus under the Constitution’s original meaning the law of nations was part of domestic law, but it was not of supreme domestic law established by Article VI nor a basis for federal jurisdiction under Article III.

This essay also considers a different “intermediate” view of the law of nations advanced by Professors Anthony J. Bellia and Bradford Clark in their important new book “The Law of Nations and the U.S. Constitution.” Bellia and Clark argue, among other things, that different parts of the law of nations had different roles under the Constitution’s original meaning. Specifically, they argue that the Constitution’s assignment to the federal government of the power to recognize foreign governments implicitly precluded states from interfering with the rights of foreign nations established by the law of nations. Thus, while the law of nations did not become part of supreme law for all purposes, the rights of recognized foreign governments – reflected for example in doctrines such as foreign sovereign immunity and the act of state doctrine – did in effect become part of supreme law, displacing contrary state law. This essay concludes that the Bellia and Clark position is not supported by evidence from the founding era. However, it further concludes that the Bellia and Clark position may be the best way to understand modern judicial practice, which appears to make foreign sovereign rights superior over state law without recognizing a full incorporation of unwritten international law into supreme domestic law.

Keywords: Customary International Law, Law Of Nations, Constitutional Law, Preemption, Textualism, Originalism

JEL Classification: K33

Suggested Citation

Ramsey, Michael D., The Constitution's Text and Customary International Law (November 19, 2017). 106 Georgetown Law Journal 1747 (2018), San Diego Legal Studies Paper No. 17-313, Available at SSRN:

Michael D. Ramsey (Contact Author)

University of San Diego School of Law ( email )

5998 Alcala Park
San Diego, CA 92110-2492
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619-260-4145 (Phone)
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