The Law of Nations as a Constitutional Obligation
Michael D. Ramsey
Does the U.S President have a constitutional obligation to comply with international law? 1That question, long debated in commentary, has new force today. The modern exigencies of the
metaphorical „war on terror‟ and the all-too-real wars in Afghanistan and Iraq pose the question
starkly: does the President have constitutional power to decide that U.S. national security requires actions that violate unwritten but commonly accepted principles arising from, for 2example, international humanitarian law and the laws of armed conflict?
Although the matter has been widely discussed, few attempts have been made to assess it strictly in terms of the historical meaning of the Constitution‟s text. Most accounts assume,
explicitly or implicitly, that changes in the nature of international relations, in international law, 3or in our understanding of law itself, call for a distinctly modern meaning. The debate has
centered principally on the modern role of the presidency, and on disputes over the meaning of Supreme Court cases decided long after the founding. This article, in contrast, pursues a textual and historical inquiry, and while it does not argue that this must control modern interpretation, it suggests that the Framers‟ solution remains comprehensible and workable in the modern era.
The question turns initially on the Constitution‟s Article II, Section 3, which directs that the President “shall take care that the laws be faithfully executed.” This clause confirmed that the U.S. President could not exercise what in England was called the „dispensing‟ or „suspensive‟ 4power, as sometimes claimed by the king: the power to suspend or override law. It was added
as the companion clause to Article II, Section 1, which gave the President the “executive Power” of the United States; although the contours of the “executive Power” are much disputed, it is relatively common ground that the executive power did not, as a general matter, include the 5“legislative” power to make (or displace) law. Taken together, Article II, Sections 1 and 3
assigned the President the power and duty to uphold and enforce laws, assuring that the President could not create, change or disregard laws.
1 E.g., Michael Glennon, Raising the Paquete Habana: Is Violation of Customary International Law by the
Executive Unconstitutional?, 80 NW. U. L. REV. 321 (1985); Agora, May the President Violate International Law?,
80 AMER. J. INT‟L L. 913 (1986); Agora, May the President Violate International Law? (con’t), 81 AMER. J. INT‟L L.
371 (1987); Arthur Weisburd, The Executive Branch and International Law, 41 VAND. L. REV. 1205 (1988). 2 Although the current President maintains that U.S. policy is to follow international law in conducting the war on terror, the Department of Justice argued in 2002, in an internal memorandum leaked to the media, that the President is not constitutionally bound by international law, such as rules against torture. See Michael Ramsey, Torturing
Executive Power, 93 GEORGETOWN L.J. 213 (2005) (describing and criticizing the memorandum). 3 The leading accounts are, moreover, almost twenty years old, and predate a substantial turn to textual analysis in foreign affairs law. See Agora, supra note 1, at 913, 923, 930; Glennon, supra note 1. For historical accounts, see
Agora, con’t, supra note 1, at 377 (essay by Jordan Paust) (arguing on the basis of Framers‟ intent that the President is bound by international law); Jules Lobel, The Limits of Constitutional Power: Conflicts between Foreign Policy
and International Law, 71 VA. L. REV. 1071 (1985) (same); contra Weisburd, supra note 1; see also Stewart Jay,
The Status of the Law of Nations in Early American Law, 42 VAND. L. REV. 819 (1989) (examining history without
reaching a definite conclusion). 4 Saikrishna Prakash, The Essential Meaning of Executive Power, 2003 U. ILL. L. REV. 701 (2003). 5 See Saikrishna Prakash & Michael Ramsey, The Executive Power over Foreign Affairs, 111 YALE L.J. 231 (2001).
Unfortunately, the drafters of the “take care” clause did not specify which “laws” the President must faithfully execute. Presumably they did not mean all “laws” – the President
would not be bound by foreign law, for example, or biblical law. But they might not have meant only laws enacted by Congress (since the text lacks that limitation expressly). In particular, the constitutional generation acknowledged a set of international rights and duties, which they called the “law of nations,” arising outside of U.S. law and yet binding, in at least some senses, on the
United States. The Constitution‟s text itself acknowledged such a system, giving Congress 6 Moreover, the existence of power to “define and punish … offenses against the law of nations.”
this law formed a central tenet of Enlightenment legal and political writing, on which eighteenth-7century Americans heavily relied. It is not implausible that, when the Framers spoke of “laws,” they meant the law of nations as well as statutory law.
Americans took law-of-nations obligations seriously, worrying that the weak national government under the Articles of Confederation (the governing document of the Union from 1781 to 1789) did not adequately ensure that the nation could and would respect its international duties. The need to strengthen the Articles‟ law-of-nations aspects played a material role in
arguments for adopting the Constitution. But while the Framers embraced the law of nations conceptually, it is unclear how they fit it into their constitutional system.
One possibility, suggested by Justice Horace Gray‟s pivotal opinion in The Paquete
Habana (1900), is that the law of nations is part of U.S. law of its own force. Gray famously claimed that “International law is part of our law, and must be ascertained and administered by
the courts of justice of appropriate jurisdiction, as often as questions of right depending upon it 8are duly presented for their determination.” He identified no text or other material
constitutional authority in support, and it is not even clear he thought he was interpreting the Constitution. Nonetheless, Gray‟s aphorism has become central – almost talismanic – to claims
that international law imposes constitutional obligations upon domestic actors, including the 9President, who is presumably bound by “our” law, albeit international in origin. In this view,
international law, though not reflected in positive enactment, is (or “is like”) federal common 10law, imposing similar obligations.
6 U.S. CONST. Art. I, Sec. 8. 7 E.g., 1 WILLIAM BLACKSTONE, COMMENTARIES ON THE LAWS OF ENGLAND 43 (1765); EMMERICH DE VATTEL,
DROIT DES GENS [Law of Nations] (Joseph Chitty ed. 1852 (1758). See PETER ONUF & NICHOLAS ONUF, FEDERAL
UNION, MODERN WORLD: THE LAW OF NATIONS IN AN AGE OF REVOLUTIONS, 1776-1814, at 11 (1993). See
ARTHUR NUSSBAUM, A CONCISE HISTORY OF THE LAW OF NATIONS 150-64 (rev. ed. 1954). 8 175 U.S. 677, 700 (1900). 9 Gray imposed an international law obligation on an executive branch officer, a naval captain during wartime. He emphasized, though, that the President‟s policy was to follow international law in conducting the war, and that the
President had not directed the acts in question. For attempts to untangle Gray‟s ambiguities, see, e.g., LOUIS
HENKIN, FOREIGN AFFAIRS AND THE U.S. CONSTITUTION 239-45 (2d ed. 1996); Glennon, supra note 1, at 348-58. 10 See especially Beth Stephens, The Law of Our Land: Customary International Law as Federal Law after Erie, 66
FORDHAM L. REV. 393 (1997); Lea Brilmayer, Federalism, State Authority and the Preemptive Power of
International Law, 1994 SUP. CT. REV. 295. On broader debates over the relationship between international law and U.S. law, see, e.g., Louis Henkin, International Law as Law in the United States, 82 MICH. L. REV. 1555 (1984);
Arthur Weisburd, State Courts, Federal Courts and International Cases, 20 YALE J. INT‟L L. 1 (1995); Curtis
Bradley and Jack Goldsmith, Customary International Law as Federal Common Law: A Critique of the Modern
Position, 110 HARV. L. REV. 815 (1997); Harold Koh, Is International Law Really State Law?, 111 HARV. L. REV.
1824 (1998); Ryan Goodman & Derek Jinks, Filartiga’s Firm Footing: International Human Rights and Federal
Common Law, 66 FORDHAM L. REV. 463 (1997); Gerald Neuman, Sense and Nonsense about Customary
On the other hand, one might suppose that the law of nations stands wholly outside U.S. law until incorporated by some domestic entity – such as Congress acting under its “define and
punish” power or the treatymakers acting under Article II, Section 2. Thirty-eight years after
Paquete Habana, the Court appeared to reverse course: Justice Brandeis declared in Erie R.R. Co.
v. Tompkins (1938), again without much textual support, that the laws applicable in U.S. courts are the laws of the individual states, “except in matters governed by the Federal Constitution or
by Acts of Congress.” There is, he said, no “transcendental body of law outside any particular 11State but obligatory within it.” Although Erie addressed domestic law and focused on
federalism rather than executive power, its implication seemed, in the eyes of some scholars, to be that the only laws cognizable in the U.S. system are positively enacted federal law (statutes and the Constitution, and, one must add, treaties) or state law. International law, on its own, seems to lie outside this system. If that is so, the President owes no constitutional obligation to it, 12except to the extent a statute or treaty adopts it.
Erie, though, left the door open to limited federal court lawmaking in areas of unique 13federal interest, and in Banco Nacional de Cuba v. Sabbatino (1964) the Court found some 14aspects of foreign affairs to be one of those areas. Sabbatino involved a rule of abstention –
when courts should decline to adjudicate acts of a foreign sovereign pursuant to the so-called “act of state” doctrine – which it applied as a rule of “federal common law” binding upon the states. Sabbatino did not explain where federal courts got authority to impose such a rule or how this conclusion squared with Erie; nor did it make any direct conclusions about international law or executive power. But the combination of Sabbatino and Paquete Habana suggested that,
notwithstanding Erie, international law might be conceived as federal common law, and thus given the constitutional status of federal law, presumably binding on the states – and the 15President.
Because Erie, Sabbatino and Paquete Habana relied more on grand jurisprudential
declarations than close analysis of the Constitution‟s text, the debate in this area likewise has tended away from the text, into the less-grounded question whether international law is or is not „federal common law.‟ In some accounts (such as Justice Gray‟s), it may be difficult to tell that
International Law: A Response to Professors Bradley and Goldsmith, 66 FORDHAM L. REV. 371 (1997); Ernest
Young, Sorting out the Debate over Customary International Law, 42 VA J. INT‟L L. 365 (2002); Daniel Meltzer,
Customary International Law, Foreign Affairs and Federal Common Law, 42 VA. J. INT‟L L. 13 (2002). For my
prior tentative thoughts, see Michael Ramsey, International Law as Part of Our Law: A Constitutional Perspective,
29 PEPP. L. REV. 187 (2001); Michael Ramsey, International Law as Non-Preemptive Federal Law, 42 VA. J. INTL L.
555 (2002). 11 304 U.S. 64, 78-79 (1938). 12 E.g., Bradley & Goldsmith, supra note 10, at 852-53; Curtis Bradley & Jack Goldsmith, International Law as
Federal Law: A Response, 111 HARV. L. REV. 2260 (1998). See Bergman v. De Sieyes, 170 F.2d 360 (2d Cir. 1948). 13 Hinderlider v. La Plata River & Cherry Creek Ditch Co., 304 U.S. 92, 110 (1938) (applying “federal common law” to resolve water law dispute between states); see also Clearfield Trust Co. v. United States, 318 U.S. 363, 367
(1943) (applying federal common law to obligations of the United States); Texas Industries v. Radcliffe Materials, 451 U.S. 630, 641 (1981) (suggesting federal common law may apply to foreign affairs matters). See Thomas
Merrill, The Common Law Powers of the Federal Courts, 52 U. CHI. L. REV. 1 (1985). 14 376 U.S. 398, 426-27 (1964). 15 E.g., HENKIN, supra note 9, at 238; Koh, supra note 10; Neuman, supra note 10; Stephens, supra note 10. See
Henry Friendly, In Praise of Erie – And the New Federal Common Law, 39 N.Y.U. L. REV. 383 (1964).
the matter is even conceived as a constitutional question. Others, while touching upon text and historical background, find these sources largely inconclusive, and devote their energy to examining pronouncements by the Supreme Court – for example, to exhaustive yet inconclusive
attempts to unravel what Justice Gray was talking about – or to modern practical exigencies.
Even within the most complete historical accounts, the focus is upon general statements of particular framers rather than the Constitution itself. As a result, we lack a comprehensive account of how the text, given its historical meaning, treated the law of nations.
Moreover, the uncompromising dichotomy apparently imposed by Erie reinforces an all-
or-nothing approach: that international law is either fully federal law or not federally cognizable law at all. That is, Erie demands that there are only two types of cognizable law – state and
federal; we must (it is said) decide which one international law is, and on that question the contending sides have engaged. While most accounts recognize that this division is not inevitable as a matter of historical meaning, and indeed is contrary to the way international law was treated through much of our history, it seems inevitable today, under the jurisprudential 16developments reflected in Erie. This pushes to the side an entirely plausible intermediate
position, which accords with the law of nations‟ status in the nation‟s early years: that international law might be “part of our law” for the purposes of some constitutional provisions and some constitutional actors, but not others.
In investigating the President‟s duty to the law of nations, this article seeks two wider goals. First, it seeks to re-focus at least part of the inquiry over the domestic status of international law upon the historical meaning of the Constitution‟s text. Second, it seeks to re-
invigorate an intermediate approach to the constitutional status of international law – affirming
that international law can be “law” of its own force for some purposes within the domestic system, yet not be “supreme Law” under Article VI, and hence not fully “federal” law as we think of it today.
The article proceeds as follows. Part I establishes important, though relatively uncontroversial, background: that the constitutional generation in America broadly agreed upon the existence (though not necessarily the content) of a body of unwritten principles, called the law of nations, governing relationships among nations; that compliance with these principles was thought important; and that they needed to be brought within the constitutional system in some affirmative manner. Part II begins the inquiry into the President‟s obligations by examining the supremacy clause of Article VI. If the law of nations fell within that clause, presumably it would bind the President; the very phrase “supreme law” indicated that no one, including the President, 17was above it. This part concludes, however, that while the written law of nations (treaties) was made part of supreme law, the unwritten law of nations was not. The language of the supremacy clause cannot be stretched to include the unwritten part, and the differential treatment of treaties,
16 See authorities cited nn. 1, 10. For scholarly defenses of various intermediate approaches, see Young, supra note
10; Weisburd, States Courts, supra note 10; Alexander Aleinikoff, International Law, Sovereignty, and American
Constitutionalism: Reflections on the Customary International Law Debate, 98 AMER. J. INT‟L L. 91 (2004). 17 See Jordan Paust, Is the President Bound by the Supreme Law of the Land? – Foreign Affairs and National
Security Reexamined, 9 HAST. CONST. L.Q. 719 (1982) (arguing for President‟s obligation to international law under
the supremacy clause).
together with concerns about the vagueness of the law of nations, suggests a deliberate decision to omit it.
The exclusion of the law of nations from supreme law leads some commentators to argue that it is not part of U.S. domestic law at all, unless incorporated by statute or treaty. If true, that would necessarily mean that the law of nations is not an obligation of the President (unless so incorporated). Part III argues, however, that this view is also mistaken, as a matter of the text‟s 18 as historical meaning. Using the Supreme Court‟s recent decision in Sosa v. Alvarez-Machain
an illustration, this part argues that the Constitution made the law of nations a source of law in 19the United States for some purposes. Although it was not implicitly incorporated into Article
VI, it was an implicit part of the law federal courts could use as a rule of decision under their “judicial power,” conveyed by Article III, Section 1. Part III further argues that nothing in the Court‟s decision in Erie, or in related changes in thinking about the nature of law, renders this view unintelligible to modern ears. In modern terms, international law could be considered federal law but not supreme law; the Constitution does not say that all federal law must be supreme. In the original design the law of nations was subordinate law; since there was no conflicting source of law, the Sosa Court could have rested its authority to apply international
law directly on the Constitution.
Part IV argues that, as a result, even though the law of nations was not made supreme law, that is insufficient to disprove a presidential duty. The President‟s duty is to “laws”, not to
“supreme laws” (a phrase that describes a relationship to other laws, not to executive power). Of
course, “laws” in this sense can only mean laws generally binding on and within the United States. But the law of nations had this status, as evidenced by its (implicit) inclusion within the judicial power of Article III, Section 1. It is hard to see how the President could generally claim independent power to order a federal court to not apply a law that court would otherwise constitutionally apply. Accepting such a power would make the President a lawmaker (or at least grant a suspensive power), contrary to the President‟s role as an executive. The President, as executive, was (except in a few narrow areas) not a lawmaker; the President was expected to conform to, not change, applicable laws – a point confirmed by the take care clause. Under the
approach advanced by this article, the law of nations would be applicable unless displaced by a superior act of sovereign lawmaking. That could be done only by a sovereign lawmaking body, which the President is not. Part IV concludes, however, that the Constitution did not make the President subject to substantial judicial oversight in the interpretation and administration of the law of nations, for that would infringe the President‟s executive power.
I. The Framers and the Law of Nations
A. The Framers’ Commitment to the Law of Nations
To begin with uncontroversial background, the constitutional generation in America recognized a set of international rights and duties they called the “law of nations.” The
18 542 U.S. 692 (2004). 19 In Sosa, plaintiff brought a claim based on international law in federal court; there was no conflicting state law, so the only question was whether international law could provide a rule of decision. The Court avoided the constitutional question by finding congressional authorization under the Alien Tort Claims Act. Id.
Constitution‟s text directly acknowledged this law: Article I, Section 8, gave Congress power to “define and punish … offenses against the law of nations.” While the Constitution did not define
the phrase, it invoked the Enlightenment conception of a system of rights and duties arising outside U.S. domestic law, from the nature of the international system, which was binding (at least in some senses) upon the United States and its citizens. As Blackstone wrote:
[A]s it is impossible for the whole race of mankind to be united in one great society, they
must necessarily divide into many; and to form separate states, commonwealths and
nations; entirely independent of each other, and yet liable to a mutual intercourse. Hence
arises a third law to regulate this mutual intercourse, called “the law of nations”; which,
as none of these states will acknowledge a superiority in the other, cannot be dictated by
either; but depends upon the rules of natural law, or upon mutual compacts, treaties, 20 leagues and agreements between these several communities.
Blackstone echoed a long line of Enlightenment writers such as Vattel, Bynkershoek, Wolff, Burlamaqui, Pufendorf, Grotius, and Rutherforth, among others, who described the legal 21relationships among nations and were well-known in eighteenth-century America. Some of
these writers, including Vattel and Wolff, explicitly called their subject “the law of nations,” and even those that did not use the phrase were commonly described as treating that subject. Vattel‟s
Law of Nations (1758) “was unrivaled among such treatises in its influence on the American 22founders.” According to Vattel, “The Law of Nations is the science which teaches the rights 23subsisting between nations or states, and the obligations correspondent to those rights.”
The law of nations was no mere academic concept in the eighteenth century. As Americans quickly learned after independence, it could be the subject of very practical diplomatic protests and threats from nations with which the United States needed to keep on good terms. In 1784, for example, in a well-known incident, a private French citizen, Charles de Longchamps, assaulted French ambassador Marbois in Philadelphia. France protested strongly, couching its objections as a matter of the law of nations, which, it said, guaranteed the 24ambassador‟s safety.
20 1 BLACKSTONE, COMMENTARIES, at 43. 21 HUGO GROTIUS, DE JURE BELLI ET PACIS (William Evats trans. 1682) ( 1625); SAMUEL PUFENDORF, DE JURE
NATURAE ET GENTIUM LIBRI OCTO (C. &W. Oldfather trans., 1934 ) (1688); JEAN JACQUES BURLAMAQUI, THE
PRINCIPLES OF NATURAL AND POLITIC LAW (Thomas Nugent trans. 1807) (1735); CORNELIUS VAN BYNKERSHOEK,
QUESTIONUM JURIS PUBLICI LIBRI DUO (Tenney Frank trans. 1930) (1737); CHRISTIAN WOLFF, JUS GENTIUM
METHODO SCIENTIFICA PERTRACTATUM (Joseph Drake trans. 1934) (1748); THOMAS RUTHERFORTH, INSTITUTES OF
NATURAL LAW (1756); VATTEL, supra note 7. 22 ONUF & ONUF, supra note 7, at 11. See Jay, supra note 3, at 823 (“An essential part of a sound legal education [in
the constitutional period in America] consisted of reading Vattel, Grotius, Pufendorf and Burlamaqui, among others.”); BERNARD BAILYN, THE IDEOLOGICAL ORIGINS OF THE AMERICAN REVOLUTION 27 (1967) (discussing
Framers‟ relationship to Enlightenment rationalism). 23 VATTEL, supra note 7, at liv. 24 DEPARTMENT OF STATE, 1 DIPLOMATIC CORRESPONDENCE 89 (1834) (Chevalier de la Luzerne to Continental
Congress, May 20, 1784); 27 JOURNALS OF THE CONTINENTAL CONGRESS 478, 503-04 (Galliard Hunt, ed., 1912).
On the law of nations protection of ambassadors, see VATTEL, supra note 7, at 371, 394; 4 BLACKSTONE, supra note
7, at 68. On the Marbois incident, see William Casto, The Federal Courts’ Protective Jurisdiction over Torts
Committed in Violation of the Law of Nations, 18 CONN. L. REV. 467 (1986).
American leaders not only acknowledged a law of nations, but took its directions seriously. Concerns about complying with the law of nations appeared often in the discourse leading to the Constitutional Convention, and in the ratification debates. A central concern was 25that the Articles‟ Congress lacked power to enforce the law of nations. When France, for
example, claimed violation of its law-of-nations rights in the Marbois incident, the Congress could do little more than refer the matter to the relevant state, Pennsylvania, and hope for the best. Leaders such as Madison, Hamilton, Randolph and Jay thought this problematic, because failure to comply with the law of nations could damage national foreign policy – perhaps even 26leading to war – and thus should be brought under national control.
Early Americans viewed the Articles‟ law-of-nations problems in tandem with parallel
problems afflicting treaty obligations. Like the unwritten law of nations, treaties were international obligations the national government owed foreign nations or individuals; leading 27writers and diplomats called treaties a branch of the law of nations. Because the Congress
lacked treaty enforcement power, it could do little to prevent treaty violations. Most prominently, states refused to accept obligations undertaken in the 1783 peace treaty with Britain. The national government tried unsuccessfully to encourage state compliance; persistent violations soured relations with Britain throughout the Articles period, and frustrated efforts to conclude additional treaty arrangements. As with the unwritten law of nations, treaty enforcement became a key argument for the new Constitution – often the two were discussed as part of a single 28argument.
25 See Michael Ramsey, The Myth of Extraconstitutional Foreign Affairs Power, 42 WM. & MARY L. REV. 379, 420-
24 (2000); FREDERICK MARKS, INDEPENDENCE ON TRIAL: FOREIGN AFFAIRS AND THE MAKING OF THE
CONSTITUTION 52-95 (1973). 26 E.g., James Madison, Vices of the Political System of the United States, 9 PAPERS OF JAMES MADISON 356-57
(1787); 1 RECORDS OF THE FEDERAL CONVENTION OF 1787, at 19 (Max Farrand, ed.) (Randolph); THE FEDERALIST,
No. 3 (Jay) (Isaac Kramnick, ed.), at 95 (“It is of high importance to the peace of America that she observe the laws of nations towards all these [European] powers, and to me it appears evident that this will be done more perfectly and punctually done by one national government than it could be either by thirteen separate States of by three or four distinct confederacies.”); 8 DOCUMENTARY HISTORY OF THE RATIFICATION OF THE CONSTITUTION 262 (public
letter of Edmund Randolph, Oct. 10, 1788) ( “in the constitutions, and laws of the several states … the law of nations is unprovided with sanctions in many cases, which deeply affect public dignity and public justice” and as the Congress lacked power “to remedy these defects,” it might be “doomed to be plunged into war, from its wretched impotency to check offenses against this law.”); THE FEDERALIST, No. 42, at 264-65 (Madison) (Articles “contain no
provision for the cases of offense against the law of nations; and consequently leave it in the power of any indiscreet member to embroil the confederacy with foreign nations.”).
Some historians stress that the constitutional generation‟s commitment to the law of nations arose from America‟ position as a relatively weak but enlightened power that could promote, and be protected by, a system of
law – rather than power relationships – among nations. See ONUF & ONUF, supra note 7, at 1-52; Jay, supra note 3,
at 839-40. 27 E.g., BLACKSTONE, COMMENTARIES, at 43; VATTEL, supra note 7, at lxv. See Thirty Hogsheads v. Boyle, 13 U.S.
191 (1814) (Marshall) (“The law of nations ... is in part unwritten, and in part conventional.”). 28 Madison complained that the Congress could not “cause infractions of treaties, or of the law of nations, to be
punished.” 1 FARRAND, supra note 26, at 316. See also id. at 19 (Randolph) (Congress “could not cause infractions
of treaties or the law of nations to be punished”); id. at 316 (Paterson) (noting “violations of the law of nations & of
treaties which if not prevented must involve us in the calamities of foreign wars”). As John Jay later recounted, “in their national capacity, the United States were responsible to foreign nations for the conduct of each state, relative to the laws of nations, and the performance of treaties; and there the inexpediency of referring all such questions to the State Courts, and particularly to the Courts of delinquent states became apparent.” Chisholm v. Georgia, 2 U.S. 419, 475 (1793). Earlier the Congress had asked states to “provide punishment for infractions of the immunity of
As an initial step, we may conclude that the constitutional generation in America generally acknowledged a set of international rights and duties called “the law of nations” that
arose outside U.S. law and regulated nations‟ “mutual intercourse,” as Blackstone put it. We can be satisfied that the Framers of the Constitution believed that compliance with this law was a duty of the nation and a key to successful foreign policy – notably absent from the Framers‟
discourse is any sustained appeal to what we would call “realism” in international relations as a value superseding the requirements of the law of nations. Their challenge, obviously, was to achieve an integration of the law of nations – written and unwritten – into the constitution of the
new federal government that had eluded the drafters of the Articles. The question, then, is how they accomplished that goal.
B. Sources and Content of the Law of Nations
It is also appropriate to briefly sketch the eighteenth-century view of the law of nations, although any such summary is necessarily oversimplified. Modern discourse often equates the eighteenth-century “law of nations” with what today we call “customary international law”: a
body of law derived from the practices of nations which nations view as imposing legal obligations. In this strictly positivist account, international law derives only from practice – it is
practice that makes law, and one could view the system as founded on tacit consent given by the 29 participating sovereigns.
The eighteenth-century view was more complex. The period lacked the commitment to positivism that characterized the next century and drove the foundation of nineteenth-century international law upon tacit consent. As Vattel put it, “the law of nations is originally no other 30than the law of Nature applied to Nations.” Blackstone had said that the law of nations
“depends upon the rules of natural law, or upon mutual compacts, treaties, leagues and
agreements between these several communities.” Leading law-of-nations treatises identified its
principles with natural law in their very titles; Burlamaqui‟s main work was “Principles of Natural and Politic Law,” and Vattel subtitled his Law of Nations “or Principles of the Law of
Nature Applied to the Conduct and Affairs of Nations and Sovereigns.”
The overriding impulse in eighteenth-century law was not positivism (as in the nineteenth century) but rationalism. Much of the idea, at least, was that just principles of international relations could be discovered through reason, from the nature and needs of the international system. Christian Wolff called his 1748 law-of-nations work “The Law of Nations According to
ambassadors and other public ministers [and] infraction of treaties and conventions to which the United States are a party.” 21 JOURNALS 1136-37 (Nov. 23, 1781). 29 See DAVID BEDERMAN, THE SPIRIT OF INTERNATIONAL LAW 14 (2002) (“The doctrine of consent generally
teaches that the common consent of states voluntarily entering the international community gives international law its validity. States … are said to be bound by international law because they have given their consent.”); id. at 94
(“We take it as an article of faith that the modern law of nations derives its legitimacy from the consent of states”); Michael Ramsey, The Empirical Dilemma of International Law, 41 SAN DIEGO L. REV. 1243, 1243-46 (2004). I
have questioned whether this account fully explains modern international law, id. at 1252-53, but it is modern
international law‟s principal rhetorical basis. In fact, modern international law may have more in common with the eighteenth-century law of nations than its rhetoric suggests. 30 VATTEL, supra note 7, at lvi.
31 as the title indicated, it was deductive rather than descriptive in a Scientific Method”;
methodology, deriving rules logically from universally-accepted first principles.
Vattel, though a bit more complicated, also saw the matter primarily one of deduction from basic principles. As Vattel described his subject at the outset, the law of nations is “that 32system of right and justice which ought to prevail between nations or sovereign states”; as he
quoted Wolff, “the law of nations certainly belongs to the law of nature: it is, therefore, on
account of its origin, called the natural, and, by reason of its obligatory force, the necessary law of nations. That law is common to all nations; and if any one of them does not respect it in her 33actions, she violates the common rights of all the others.” “We must,” he declared, “apply to
nations the rules of the law of nature, in order to discover what their obligations are, and what their rights: consequently, the law of Nations is originally no other than the law of Nature 34applied to Nations.” As a result, “we call that the Necessary Law of Nations which consists on the application of the law of nature to Nations. It is Necessary because nations are absolutely bound to observe it….Since therefore the necessary law of nations consists in the application of
the law of nature to states – which law is immutable, as being founded on the nature of things, 35and particularly on the nature of man….” This of course involved some difficulty of proof, but,
Vattel said, he would “advance nothing as a principle that will not be readily admitted by every 36sensible man.”
Leaders of the constitutional generation in America echoed Vattel‟s appeal to reason. James Iredell said that “the only way to ascertain the duties which one nation owes another, is to
enquire what reason dictates, that attribute which the Almighty has bestowed upon all mankind 37for the ultimate guide and director of their conduct.” James Wilson called it “the law of nature 38applied to states and sovereigns.” U.S. Supreme Court Justice Joseph Story wrote as late as
31 WOLFF, supra note 21. 32 VATTEL, supra note 7, at viii. 33 Id. at xi. 34 Id. at lvii. Vattel added that the law of nations was a distinct branch of inquiry, because the law of nature did not always apply to nations in the same way it did to individuals. Id. 35 Id. at lviii. Following Wolff and Grotius, Vattel recognized a derivative category of rules, confusingly called the “voluntary” law of nations. Generally speaking, the idea was that nations could not insist upon the strict justice of
the law of nature, because their mutual interactions required certain “modifications” or accommodations to prevent constant conflict. These rules, though, also flowed deductively from the nature of the international system and (despite their name) did not depend on actual consent. As Vattel explained, “I shall, in the course of this work, be able to prove that all the modifications [from the natural law of individuals] … are deducible from the natural liberty
of nations, from the attention due to their common safety, from the nature of their mutual correspondence, their reciprocal duties, and the distinctions of their various rights.” Id. at xiv. He summarized: “The necessary and the
voluntary laws of nations are therefore both established by nature, but each in a different manner: the former as a sacred law which nations and their sovereigns are bound to respect and follow in all their actions; the latter, as a rule which the general welfare and safety oblige them to admit in their transactions with each other.” Id. at xv. Vattel
distinguished both categories from a third he called the “arbitrary” law of nations, which “proceeds from the will or consent of nations” – in this category he placed written and tacit agreements. Id. 36 Id., at xvi. See NUSSBAUM, supra note 7 (discussing eighteenth-century law-of-nations theory). 37 Iredell, Charge to South Carolina Grand Jury (May 12, 1794), quoted in Jay, supra note 3, at 823. As Professor
Jay confirms, “In the eighteenth century a consensus existed that the law of nations rested in large measure on natural law.” Id. at 822. 38 JAMES WILSON, 1 WORKS OF JAMES WILSON 147 (Robert McCloskey, ed., 1967). See also 2 id. at 813 (“the law
of nations has its foundation in the principles of natural law, applied to states; and in voluntary institutions, arising from custom or convention.”).
1822 that the law of nations “may be fairly deduced by correct reasoning from the rights and 39duties of nations, and the nature of moral obligation.”
Appeals to practice, though, played a larger actual role than Vattel‟s theoretical
discussion suggested. Vattel himself admitted that his arguments were more persuasive if he could “show that the practice of nations is conformable to the principles laid down,” and as 40arguments developed appeals to the usual way of doing things carried significant weight. At
another point Vattel described the system in part as resting on “certain maxims and customs, consecrated by long use, and observed by nations in their mutual intercourse with each other as a 41kind of law.” Blackstone emphasized this hybrid character in writing of “a system of rules, deducible by natural reason, and established by universal consent among the civilized inhabitants 42of the world.” And when Americans sought to put the law of nations into practice, reliance on custom became more pronounced. As Jefferson later said, the “principles of the law of nations” 43were “evidenced by the Declarations, Stipulations and Practice of every civilized Nation.” At
the risk of some oversimplification, one might say that practice was evidence of the natural state 44of nations.
In sum, the eighteenth-century law of nations had complex and not fully articulable foundations. It mixed Enlightenment rationalism with older reliance on tradition and the already-rising ideas that became nineteenth-century positivism. The upshot was that while some principles were well-accepted and understood at a level of considerable detail, others were not. Indeed, its substantial foundation on rationalism meant that its rules were often not easily demonstrated. As Blackstone wrote of determining natural law by reason:
And if our reason were always, as in our first ancestor before his transgression, clear and
perfect, unruffled by passions, unclouded by prejudice, unimpaired by disease or
intemperance, the task would be pleasant and easy; we should need no other guide but
this. But every man now finds the contrary in his own experience; that his reason is 45corrupt, and his understanding full of ignorance and error.
Not surprisingly, authorities frequently disagreed upon the right rule, and equally unsurprisingly, often appealed to practice (as well as reason) in support. But since the system lacked an internal 46rank of priorities, it was hard, in such circumstances, to say who was right.
39 United States v. La Jeune Eugienie, 26 F. Cas. 832, 846 (C.C. D. Mass. 1822). See Jay, supra note 3, at 824
(writers described law of nations as “a system of rules capable of rational explication”); NUSSBAUM, supra note 7. 40 VATTEL, supra note 7, at xvii. 41 Id. at lxv. 42 4 BLACKSTONE, supra note 7, at 66. 43 Jefferson to Pinckney, May 7, 1793, 7 WORKS OF JEFFERSON 314. 44 Practice also established what Vattel called the “arbitrary” of laws based on tacit consent between particular sovereigns. See n.35. 45 1 BLACKSTONE, COMMENTARIES, at 41. 46 See, for example, the debate over whether a formal declaration of war was required prior to initiating hostilities. Numerous authorities – including Vattel, Burlamaqui, Grotius and Wolff – claimed on the basis of reason that such a
declaration was required by the law of nations. But at least two major authorities, Bynkershoek and Rutherforth, denied it, and they had substantial practice on their side, since prior declarations were not often used. It is hard to say who was “right” in this debate. See Michael Ramsey, Textualism and War Powers, 69 U. CHI. L. REV. 1543,