The Constitutional Status of Customary International Law

Section on Constitutional Law
Panel on the U.S. Constitution in Global Perspective
San Francisco, CA, January 6, 2011

The Constitutional Status of Customary International Law

Michael D. Ramsey
Professor of Law, University of San Diego Law School

In my remarks, I will explore from a constitutional perspective the aphorism,
most prominently associated with the case of The Paquete Habana, that “international
law is part of our law.

Unlike treaties, customary international law receives little mention in the
Constitution – the only direct reference to it is in Article I, Section 8, giving Congress the
power to define and punish it. This relative silence has led one group of academic
commentators to argue that (despite Paquete Habana) customary international law is not
part of our law until Congress (or state law) makes it so. Another group of academic
commentators sharply disagrees, and instead sees customary international law
permeating the entire constitutional system: as part of “our law” – that is, U.S. federal
law – it should trump state law, provide federal jurisdiction, provide a federal cause of
action, and perhaps constrain federal executive and even congressional power.

This debate in modern practice focuses in particular on the viability of claims
brought under the federal Alien Tort Statute, which gives federal courts jurisdiction over
claims brought by aliens for torts committed in violation of international law, but does
not provide a cause of action for such claims, or otherwise identify the sorts of claims
that may be brought. The Supreme Court wrestled inconclusively with this statute in
Sosa v. Alvarez-Machain in 2004, and it seems likely to return to the Court sometime
soon (although the Court denied two high-profile cert. petitions last year in the Talisman
and Pfizer cases).

To engage in some shameless self-promotion, I have a co-edited book (with
David Sloss of Santa Clara Law School and William Dodge of Hastings Law School)
coming out later this year that examines the Supreme Court’s historical use of
international law in its decisions. What emerges from this study regarding this issue is
that courts historically pursued a middle ground in which customary international law
formed a background source of law when domestic sources run out.

First, courts historically applied customary international law as a rule of decision
where enacted state and federal law did not apply; this occurred principally in overseas

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cases, like Paquete Habana itself, which involved the seizure of fishing boats in a
blockade of Cuba. Although Paquete Habana was decided in 1900, it followed a
practice dating to the Court’s early decisions in Glass v. The Sloop Betsey and Talbot v.
Jansen in the 1790s. Second, courts interpreting ambiguous statutes used what came to
be called the Charming Betsy canon – named after an 1804 case – to construe such
statutes not to violate customary international law (while acknowledging that a clear
statute would take precedence).

Thus courts historically rejected the view that customary international law must
be enacted to have force in domestic law. But courts gave customary international law
only a modest role. We found no cases of customary international law overriding
enacted state or federal law, conveying federal jurisdiction, or otherwise operating as
supreme federal law. Thus courts historically followed neither of the contending modern
academic views.

Despite the Constitution’s silence on customary international law, this modest
approach has a constitutional basis, although courts have not made it explicit. Eighteenth-
century English courts used the law of nations, as unwritten international law was then
called, as a rule of decision in common law. And they construed ambiguous statutes not
to deviate from common law or to operate unreasonably (which Alexander Hamilton
successfully argued in the 1784 case Rutgers v. Waddington included that statutes not
conflict with the law of nations). The U.S. Constitution, written against the background
of English judicial practice, gave U.S. courts “the judicial Power” in Article III, Section 1
– a power that in eighteenth-century terms thus encompassed the modest judicial use of
customary international law familiar from English law.

As a result, neither the Glass/Talbot line of cases directly applying unenacted
customary international law, nor the Charming Betsy interpretive rule is constitutionally
mandated: they are in a sense sub-constitutional law. But they are constitutionally
permitted, as part of U.S. courts’ textual “judicial Power” and as a matter of longstanding
judicial practice dating to the early post-ratification period.

In conclusion, returning to modern debates, the basic challenge of the Alien Tort
Statute seems less formidable. The Supreme Court tied itself in knots over the question
to what extent U.S. courts can entertain suits based solely on the unenacted law of
nations, ultimately finding – for unclear reasons – that courts could do so in narrow
circumstances; despite, or perhaps because of, the Court’s treatment in Sosa, that
controversy continues unabated. The textual/historical approach suggests it is not so hard
a question as the Court made it appear. Where enacted law does not apply, there should
be no constitutional barrier to courts applying customary international law (if they
otherwise have jurisdiction to hear the case). The power does not need to come from
Congress, because it comes from Article III. But courts are not obligated to do so, so the
caution the Sosa Court expressed is also constitutionally justified.

At the same time, the textual/historical approach suggests that broader assertions
of the constitutional status of customary international law are – like the very narrow ones

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– more difficult to sustain. Making customary international law supreme over state (or
federal) law requires reading it into the Supremacy Clause (or giving it supreme status
despite its absence from that clause) and according it a status that judicial decisions
historically did not give it. Making customary international law part of federal law for
jurisdictional purposes requires reading it into the “laws of the United States” in Article
III, Section 2 in a way that nineteenth-century cases seemed not to accept. Even making
it binding on the executive branch, perhaps a claim more firmly grounded in text and
history, requires an extrapolation from the take-care clause and rests only on dicta rather
than actual holdings in early cases. At minimum, these positions remain contested – but
their contested status should not undermine the more modest judicial use of customary
international law that does have firm textual and historical grounding.

__________________________

Note: In the question/comment section, the following important points were raised –

First, one question pressed on the claim that courts’ application of customary
international law is permitted but not required. My answer is that Article III, Section
1 – like Article I, Section 1 and Article II, Section 1 – is a grant of power not an
obligation. Except perhaps in a few unusual and narrow circumstances, Congress has no
constitutional obligation to use its Article I, Section 1 power to regulate; the President’s
obligation to enforce the law arises from the take care clause, not from the grant of
executive power in Article II, Section 1. Similarly courts have no Article III, Section 1
obligation to exercise their power. Courts do have (like other U.S. actors) an obligation
to uphold the Constitution and, by extension, laws and treaties made pursuant to the
Constitution’s grants of power. But customary international law, in contrast, is not a
constitutional obligation.

A second question asked about the relevance of the Court’s 1938 decision in Erie RR.
Co. v Tompkins, which declared that all law applied in federal courts must be state law,
enacted federal law or constitutional law. This decision raises difficult questions for
customary international law, because it purported to abolish the category of general
common law, previously applied by the Supreme Court under the 1842 decision Swift
v. Tyson. Because nineteenth century courts understood their application of customary
international law as part their application of general common law, Erie’s abolition of
that category appeared to leave customary international law’s status much in doubt. My
answer here – while endorsing fully this account of Erie – is to urge us not to read too
much into that decision. (This was a mistake the Supreme Court made in Sosa, and it
rendered that decision more difficult than it needed to be). Erie was not a case about
customary international law at all (it involved a railway accident in Pennsylvania, with no
international parties). Moreover, Erie was about the federal courts’ ability (or inability)
to depart from applicable state law, whether enacted law or common law; it concluded
federal courts generally lacked that ability. But the modest application of customary
international law, as reflected in Glass, Talbot, Paquete Habana and today in most Alien
Tort suits, does not involve displacement of state law, because these cases arise where

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state law does not apply. Thus it seems a mistake to try to coax out of Erie a definitive
holding with respect to a legal and factual situation remote from anything the Erie Court
considered.

Finally, a comment suggested that customary international law could be called
a “resource” to which U.S. courts could turn to resolve cases when other more directly
binding sources of domestic law were inconclusive; I agreed that this phrase aptly
captured the way courts historically had viewed it.

__________________________

References:

International Law in the U.S. Supreme Court: Continuity and Change (David L.
Sloss, Michael D. Ramsey and William S. Dodge, eds., Cambridge Univ. Press 2011)
(forthcoming), Chapters 1, 3, 7 and 11.

Curtis A. Bradley & Jack L. Goldsmith, Foreign Relations Law: Cases and Materials (3rd
ed. Aspen 2008), Chapter 7.

Michael D. Ramsey, The Constitution’s Text in Foreign Affairs (Harvard Univ. Press
2007), Chapters 17-18.

Sosa v. Alvarez-Machain, 542 U.S. 692 (2004)
Erie RR. Co. v. Tompkins, 304 U.S. 64 (1938)
The Paquete Habana, 175 U.S. 677, 700 (1900)
Swift v. Tyson, 41 U.S. 1 (1842)
Talbot v. Jansen, 3 U.S. 133 (1795)
Glass v. The Sloop Betsey, 3 U.S. 6 (1794)
Murray v. The Schooner Charming Betsy, 6 U.S. 64 (1804)

Rutgers v. Waddington (New York Mayor’s Court, 1784), reprinted in Julius Goebel, Jr.,
The Law Practice of Alexander Hamilton: Documents and Commentary, vol. 1, pp. 282-
419 (1964).

William Blackstone, Commentaries on the Laws of England, vol. 4, pp. 66-73 (1769).