Amicus Curiae Brief — Cisco Systems, Inc., et al., Petitioners v. Doe I, et al.
Supreme Court briefMar 27, 2026
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No. 24-856
IN THE
Supreme Court of the United States
————
CISCO SYSTEMS, INC., ET AL.,
Petitioners,
v.
DOE I, ET AL.,
Respondents.
————
On Writ of Certiorari
to the United States Court of Appeals
for the Ninth Circuit
————
BRIEF FOR INTERNATIONAL LAW SCHOLARS
AS AMICI CURIAE IN SUPPORT
OF RESPONDENTS
————
ROBERT K. KRY
Counsel of Record
JACKSON A. MYERS
MOLOLAMKEN LLP
The Watergate, Suite 500
600 New Hampshire Ave., N.W.
Washington, D.C. 20037
(202) 556-2000
rkry@mololamken.com
Counsel for Amici Curiae
TABLE OF CONTENTS
Page
Interest of Amici Curiae ............................................
Summary of Argument ...............................................
Argument ......................................................................
I. Under This Court’s Precedents, Whether
Aiding and Abetting Is Actionable Under
the Alien Tort Statute Is Determined by
Customary International Law.......................
II. Customary International Law’s
Prohibition Against Aiding and Abetting
Human Rights Violations Meets the Sosa
Standard ...........................................................
A. The Prohibition Against Aiding and
Abetting Is Generally Accepted.............
B. The Prohibition Against Aiding and
Abetting Is Specifically Defined ............
1. Actus Reus ...........................................
2. Mens Rea ..............................................
III. International Law Allows the United
States To Impose Civil Liability for
Aiding and Abetting Human Rights
Violations ..........................................................
Conclusion .....................................................................
(i)
1
5
7
7
9
9
15
15
17
21
24
ii
TABLE OF AUTHORITIES
Page(s)
CASES
Aziz v. Alcolac, Inc.,
658 F.3d 388 (4th Cir. 2011) .............................. 20
Banco Nacional de Cuba v. Sabbatino,
376 U.S. 398 (1964) ............................................. 22
Jesner v. Arab Bank, PLC,
584 U.S. 241 (2018) .......................................... 5, 7-9
Presbyterian Church of Sudan v.
Talisman Energy, Inc.,
582 F.3d 244 (2d Cir. 2009) ............................ 19, 20
Sosa v. Alvarez-Machain,
542 U.S. 692 (2004) ................. 5-9, 14, 15, 21, 23, 24
STATUTES
28 U.S.C. § 1350 ...................................... 5-9, 21, 23, 24
TREATIES AND INTERNATIONAL
AGREEMENTS
Agreement for the Prosecution
and Punishment of the Major War
Criminals of the European Axis and
Charter of the International Military
Tribunal, Aug. 8, 1945, 59 Stat. 1544,
82 U.N.T.S. 279 ............................................... 9, 10
Control Council Law No. 10,
1 Enactments and Approved Papers of
the Control Council and Coordinating
Committee: Allied Control Authority,
Germany–1945, at 309 (1946) ........................... 10
iii
TABLE OF AUTHORITIES—Continued
Page(s)
Convention Against Torture and Other
Cruel, Inhuman or Degrading
Treatment or Punishment,
Dec. 10, 1984, S. Treaty Doc.
No. 100-20, 1465 U.N.T.S. 85 ............................ 14
Convention on the Prevention and
Punishment of the Crime of Genocide,
Dec. 9, 1948, 102 Stat. 3045,
78 U.N.T.S. 277 .................................................. 14
Rome Statute of the International
Criminal Court, July 17, 1998,
2187 U.N.T.S. 90 ...................................... 13, 20, 21
Statute of the International Criminal
Tribunal for the Former Yugoslavia,
in Report of the Secretary General
Pursuant to Paragraph 2 of Security
Council Resolution 808,
U.N. Doc. S/25704 (May 3, 1993) ........... 11, 12, 23
Statute of the International Tribunal
for Rwanda (Nov. 8, 1994), in Security
Council Resolution 955 annex
(Nov. 8, 1994) ................................................... 12, 23
Updated Statute of the International
Criminal Tribunal for the Former
Yugoslavia (July 7, 2009)................................... 12
INTERNATIONAL DECISIONS
Case Concerning Application of the
Convention on the Prevention and
Punishment of the Crime of Genocide
(Bosnia v. Serbia), 2007 I.C.J. 43
(Feb. 26, 2007) ....................................................
23
iv
TABLE OF AUTHORITIES—Continued
Page(s)
The Einsatzgruppen Case (Trial of Otto
Ohlendorf and Others), 4 Trials of War
Criminals Before the Nuernberg
Military Tribunals Under Control
Council Law No. 10, at 411 (1952) ......... 10, 16, 18
I.G. Farben Case, 8 Trials of War
Criminals Before the Nuernberg
Military Tribunals Under Control
Council Law No. 10, at 1081 (1952) ................. 19
Judgment of the International Military
Tribunal, 1 Trial of the Major War
Criminals Before the International
Military Tribunal 171 (1947) ............................ 11
Prosecutor v. Aleksovski,
IT-95-14/1-A, Appeals Judgment
(ICTY 2000) ........................................................ 16
Prosecutor v. Blagojeviþ,
IT-02-60-A, Appeals Judgment
(ICTY 2007) ..................................................... 12, 17
Prosecutor v. Blaškiþ,
IT-95-14-A, Appeals Judgment
(ICTY 2004) ..................................................... 12, 15
Prosecutor v. Furundžija,
IT-95-17/1, Trial Judgment
(ICTY 1998) .............................................. 12, 16, 18
Prosecutor v. Kalimanzira,
ICTR-05-88-A, Appeals Judgment
(ICTR 2010) ..................................................... 17, 19
Prosecutor v. Karera,
ICTR-01-74-A, Appeals Judgment
(ICTR 2009) ........................................................ 13
v
TABLE OF AUTHORITIES—Continued
Page(s)
Prosecutor v. Kayishema,
ICTR-95-1-A, Appeals Judgment
(ICTR 2001) ........................................................ 13
Prosecutor v. Krnojelac,
IT-97-25-A, Appeals Judgment
(ICTY 2003) ........................................................ 18
Prosecutor v. Kunarac,
IT-96-23 & IT-96-23/1-A, Appeals
Judgment (ICTY 2002) ..................................... 14
Prosecutor v. KvoĀka,
IT-98-30/1-A, Appeals Judgment
(ICTY 2005) ..................................................... 12, 17
Prosecutor v. Lukiþ,
IT-98-32/1-A, Appeals Judgment
(ICTY 2012) .............................................. 12, 16, 17
Prosecutor v. Mrkšiþ,
IT-95-13/1-A, Appeals Judgment
(ICTY 2009) ..................................................... 12, 17
Prosecutor v. Muhimana,
ICTR-95-1B-A, Appeals Judgment
(ICTR 2007) .............................................. 13, 16, 18
Prosecutor v. Nahimana,
ICTR-99-52-A, Appeals Judgment
(ICTR 2007) ........................................................ 13
Prosecutor v. Ndahimana,
ICTR-01-68-A, Appeals Judgment
(ICTR 2013) .............................................. 16, 18, 19
Prosecutor v. Ntagerura,
ICTR-99-46-A, Appeals Judgment
(ICTR 2006) .............................................. 13, 16, 17
vi
TABLE OF AUTHORITIES—Continued
Page(s)
Prosecutor v. Ntakirutimana,
ICTR-96-10-A & ICTR-96-17-A,
Appeals Judgment (ICTR 2004) ............ 13, 16, 18
Prosecutor v. Ntawukulilyayo,
ICTR-05-82-A, Appeals Judgment
(ICTR 2011) ........................................ 13, 16, 18, 19
Prosecutor v. Nyiramasuhuko,
ICTR-98-42-A, Appeals Judgment
(ICTR 2015) .............................................. 13, 16, 17
Prosecutor v. Popoviþ,
IT-05-88-A, Appeals Judgment
(ICTY 2015) ........................................ 12, 15, 17, 19
Prosecutor v. Rukundo,
ICTR-2001-70-A, Appeals Judgment
(ICTR 2010) ........................................ 13, 16, 18, 19
Prosecutor v. Šainoviþ,
IT-05-87-A, Appeals Judgment
(ICTY 2014) ..................................................... 15, 17
Prosecutor v. Seromba,
ICTR-01-66-A, Appeals Judgment
(ICTR 2008) ........................................................ 16
Prosecutor v. Simiþ,
IT-95-9-A, Appeals Judgment
(ICTY 2006) ..................................................... 12, 17
Prosecutor v. Stanišiþ,
IT-03-69-A, Appeals Judgment
(ICTY 2015) ........................................................ 15
Prosecutor v. Tadiþ,
IT-94-1-A, Appeals Judgment
(ICTY 1999) ........................................................ 18
vii
TABLE OF AUTHORITIES—Continued
Page(s)
Prosecutor v. Vasiljeviþ,
IT-98-32-A, Appeals Judgment
(ICTY 2004) ........................................................ 12
Reservations to the Convention on
Prevention and Punishment of the
Crime of Genocide, Advisory Opinion,
1951 I.C.J. 15 (May 28, 1951) ............................ 14
United States v. Flick, 6 Trials of War
Criminals Before the Nuernberg
Military Tribunals Under Control
Council Law No. 10, at 1187 (1952) .............. 10, 18
United States v. von Weizsaecker
(The Ministries Case), 14 Trials of
War Criminals Before the Nuernberg
Military Tribunals Under Control
Council Law No. 10, at 314 (1952) ................... 19
The Zyklon B Case (Trial of Bruno Tesch
and Two Others), 1 Law Reports of
Trials of War Criminals 93 (1947).......... 10, 17, 18
OTHER AUTHORITIES
Aiding and Abetting in International
Criminal Law, Yale Law School Lillian
Goldman Law Library Documents
Collection Center, https://documents.
law.yale.edu/aiding-and-abetting-cases .......... 13
W. Blackstone, Commentaries
on the Laws of England (1769) ..................... 7, 23
Brief for David Scheffer as Amicus
Curiae, Presbyterian Church of
Sudan v. Talisman Energy, Inc.,
No. 09-1262 (May 19, 2010) ............................... 20
viii
TABLE OF AUTHORITIES—Continued
Page(s)
Eileen Denza, The Relationship Between
International and National Law,
in International Law 411 (Malcolm
D. Evans ed., 3d ed. 2010) ................................ 22
Oona A. Hathaway, Alexandra Francis,
Aaron Haviland, Srinath Reddy
Kethireddy & Alyssa Yamamoto,
Aiding and Abetting in International
Criminal Law, 104 Cornell
L. Rev. 1593 (2019)................................... 9, 13, 21
Louis Henkin, Foreign Affairs and
the United States Constitution
(2d ed. 1996) ........................................................ 22
Int’l Law Comm’n, Draft Articles
on Responsibility of States for
Internationally Wrongful Acts,
with Commentaries, Report of the
International Law Commission on
the Work of Its Fifty-Third Session,
U.N. Doc. A/56/10 (2001) ................................... 23
Chimène I. Keitner, Conceptualizing
Complicity in Alien Tort Cases,
60 Hastings L.J. 61 (2008) ................................ 22
Principles of International Law
Recognized in the Charter of
the Nürnberg Tribunal and in the
Judgment of the Tribunal, Report
of the International Law Commission
on the Work of Its Second Session,
U.N. Doc. A/1316 (1950) .................................... 11
Restatement (Third) of U.S. Foreign
Relations Law (1987) ......................................... 22
ix
TABLE OF AUTHORITIES—Continued
Page(s)
Security Council Resolution 827
(May 25, 1993) .....................................................
Security Council Resolution 955
(Nov. 8, 1994) ......................................................
11
12
IN THE
Supreme Court of the United States
————
NO. 24-856
CISCO SYSTEMS, INC., ET AL.,
Petitioners,
v.
DOE I, ET AL.,
Respondents.
————
On Writ of Certiorari
to the United States Court of Appeals
for the Ninth Circuit
————
BRIEF FOR INTERNATIONAL LAW SCHOLARS
AS AMICI CURIAE IN SUPPORT
OF RESPONDENTS
————
INTEREST OF AMICI CURIAE 1
Amici curiae are scholars of international law. They
have an interest in the proper application of customary international law by domestic courts, including the customary international law on aiding and abetting.
E. Tendayi Achiume is Professor of Law at Stanford
Law School and the former U.N. Special Rapporteur on
Contemporary Forms of Racism, Racial Discrimination,
Pursuant to this Court’s Rule 37.6, amici state that no counsel for
any party authored this brief in whole or in part, that no such counsel
or party made a monetary contribution intended to fund the preparation or submission of the brief, and that no person other than amici or
their counsel made a monetary contribution intended to fund the preparation or submission of this brief. Institutional affiliation listings are
for identification purposes only and do not imply the institution’s endorsement of the brief.
1
2
Xenophobia and Related Intolerance. In 2023, she was
awarded a MacArthur Fellowship.
Philip G. Alston is John Norton Pomeroy Professor of
Law at New York University School of Law, the former
Editor-in-Chief of the European Journal of International
Law, and the former U.N. Special Rapporteur on Extrajudicial Executions.
Lori Fisler Damrosch is Hamilton Fish Professor of
International Law and Diplomacy at Columbia Law School.
She is a former Editor-in-Chief of the American Journal
of International Law and a former President of the American Society of International Law.
Laura A. Dickinson is Lyle T. Alverson Professor of
Law at George Washington University Law School. She
is a board member of the U.S. Branch of the International
Society for Military Law and the Law of War and formerly
served as Special Counsel to the U.S. Department of Defense General Counsel.
William S. Dodge is Lobingier Professor of Comparative Law and Jurisprudence at George Washington University Law School. He served as a Reporter for the first
phase of the American Law Institute’s Restatement
(Fourth) of the Foreign Relations Law of the United
States (2018) and currently serves as a Reporter for its
second phase.
Mark A. Drumbl is Class of 1975 Alumni Professor of
Law and Director of the Transnational Law Institute at
Washington and Lee University School of Law. He serves
as the Editor-in-Chief of the International Criminal Law
Review.
Jean Galbraith is Professor of Law at the University of
Pennsylvania, Carey Law School. She is a member of the
Board of Editors of the American Journal of International
3
Law and a former Associate Legal Officer at the International Criminal Tribunal for the former Yugoslavia.
Richard J. Goldstone is a retired Justice of the Constitutional Court of South Africa. From 1994 to 1996, he
served as the first prosecutor of the International Criminal Tribunal for the former Yugoslavia and of the International Criminal Tribunal for Rwanda.
Oona A. Hathaway is Gerard C. and Bernice Latrobe
Smith Professor of International Law at Yale Law School.
She currently serves as a Reporter for the second phase
of the American Law Institute’s Restatement (Fourth) of
the Foreign Relations Law of the United States and is
President-Elect of the American Society of International
Law.
Derek Jinks is A.W. Walker Centennial Chair in Law
at the University of Texas School of Law. He is a Distinguished Scholar at the Robert S. Strauss Center for International Security and Law at the University of Texas and
formerly served as the Charles H. Stockton Professor of
International Law at the U.S. Naval War College.
Harold Hongju Koh is Sterling Professor of International Law and former Dean at Yale Law School. He has
served as Legal Adviser (2009-2013) and Senior Adviser
(2021) at the Office of Legal Adviser and as Assistant Secretary for Democracy, Human Rights, and Labor (19982001) at the U.S. Department of State.
Saira Mohamed is Agnes Roddy Robb Chair in Jurisprudence, Ethics, and Social Responsibility and Professor
of Law at the University of California, Berkeley, School of
Law. She is a member of the Board of Editors of the International Criminal Law Review and a former Vice President of the American Society of International Law.
4
Sean D. Murphy is Manatt /Ahn Professor of International Law at George Washington University Law School.
He is a former President of the American Society of International Law and a former member of the U.N. International Law Commission, serving as its Special Rapporteur
for crimes against humanity. He is currently a U.N. expert for the negotiation of a Convention on Prevention and
Punishment of Crimes against Humanity.
Jens David Ohlin is the Allan R. Tessler Dean and Professor of Law at Cornell Law School. He is the author
of International Law: Evolving Doctrine and Practice
(3d ed. 2025) and a co-editor of The Laws and Principles
of Secondary Liability (Cambridge Univ. Press forthcoming 2026).
Steven R. Ratner is Bruno Simma Collegiate Professor
of Law at the University of Michigan Law School and
Director of the University of Michigan Donia Human
Rights Center. He has served on expert commissions of
the United Nations regarding accountability for largescale human rights violations in Cambodia, Sri Lanka,
and Ethiopia.
Leila Sadat is James Carr Professor of International
Criminal Law at Washington University School of Law.
She served as Special Adviser on Crimes Against Humanity to the International Criminal Court Prosecutor from
2012 to 2023 and was recently appointed as a U.S. expert
to the OSCE Moscow Mechanism.
Michael P. Scharf is Associate Dean for Global Legal
Studies and Joseph C. Hostetler—BakerHostetler Professor of Law at Case Western Reserve University School
of Law. He serves as the President of the American
Branch of the International Law Association and the Managing Director of the Public International Law & Policy
Group.
5
Ralph G. Steinhardt is Lobingier Professor Emeritus
of Comparative Law and Jurisprudence at George Washington University Law School. He co-founded the Program in International Human Rights Law at New College,
Oxford, and was the founding Chair of the Center for Justice and Accountability.
Edward T. Swaine is Charles Kennedy Poe Research
Professor at George Washington University Law School.
He served as a Reporter for the first phase of the American Law Institute’s Restatement (Fourth) of the Foreign
Relations Law of the United States (2018).
Alex Whiting is Professor of Practice at Harvard Law
School. He is a former prosecutor at the U.S. Department
of Justice and a former international criminal prosecutor
at the International Criminal Tribunal for the former
Yugoslavia, the International Criminal Court, and the
Kosovo Specialist Prosecutor’s Office.
SUMMARY OF ARGUMENT
In Sosa v. Alvarez-Machain, 542 U.S. 692 (2004), this
Court recognized an implied cause of action under the
Alien Tort Statute (“ATS”), 28 U.S.C. § 1350, for claims
“based on the present-day law of nations” if those claims
“rest on a norm of international character accepted by the
civilized world and defined with a specificity comparable
to the features of the 18th-century paradigms” with which
the First Congress was familiar. 542 U.S. at 725. In Jesner
v. Arab Bank, PLC, 584 U.S. 241 (2018), the plurality
articulated a two-step test. First, a plaintiff must “demonstrate that the alleged violation is ‘of a norm that is specific, universal, and obligatory.’ ” Id. at 257-258 (plurality)
(quoting Sosa, 542 U.S. at 732). Second, a court must
determine “whether allowing th[e] case to proceed under
the ATS is a proper exercise of judicial discretion.” Id. at
258. Amici focus on the first step and argue that the pro-
6
hibition on aiding and abetting violations of international
law is itself a “specific, universal, and obligatory” norm
under customary international law.
Neither Petitioners nor the United States as amicus
curiae dispute that proposition. But two of the amici supporting Petitioners do. Amicus Washington Legal Foundation (“WLF”) argues “there is no universal standard for
civil aiding-and-abetting liability, much less one that is
‘accepted by the civilized world’ and defined with the specificity Sosa requires.” WLF Br. 2 (quoting Sosa, 542 U.S.
at 725). WLF further draws a distinction between international criminal liability for aiding and abetting and civil
liability under the ATS. Id. at 6. The U.S. Chamber of
Commerce and its co-amici, meanwhile, contend that
“recognizing a cause of action under the ATS for aidingand-abetting liability expands the ATS far beyond the
party in violation of international law itself.” Chamber Br. 6.
Those assertions are mistaken. The prohibition against
aiding and abetting violations of international law is both
generally accepted and specifically defined. WLF’s distinction between civil and criminal liability misunderstands how international law works: Whereas international law establishes binding norms, each nation decides
for itself whether and how to impose liability for violations
of such norms. The U.S. did so in the ATS, choosing to
impose civil liability for “tort[s] * * * in violation of the law
of nations.” 28 U.S.C. § 1350. And recognizing a cause of
action for aiding and abetting does not expand liability beyond the party violating international law, because aiding
and abetting is itself a violation of international law. In
short, aiding and abetting human rights violations is a
tort in violation of “the present-day law of nations * * *
accepted by the civilized world and defined with a specificity comparable to the features of the 18th-century para-
7
digms.” Sosa, 542 U.S. at 725. It is therefore actionable
under Sosa.
ARGUMENT
I. UNDER THIS COURT’S PRECEDENTS, WHETHER AIDING
AND ABETTING IS ACTIONABLE UNDER THE ALIEN
TORT STATUTE IS DETERMINED BY CUSTOMARY
INTERNATIONAL LAW
As codified today, the Alien Tort Statute provides:
“The district courts shall have original jurisdiction of any
civil action by an alien for a tort only, committed in violation of the law of nations or a treaty of the United States.”
28 U.S.C. § 1350. By referring to the “law of nations,” the
statutory text makes clear that the ATS’s applicability
depends on whether the tort alleged violates customary
international law.
In Sosa v. Alvarez-Machain, 542 U.S. 692 (2004), this
Court elaborated on the kinds of torts that are actionable
under the ATS. The Court observed that the First Congress likely had three such torts in mind when it enacted
the statute: violation of safe conducts, infringement of ambassadors’ rights, and piracy. See id. at 720. These were
“offenses against the law of nations addressed by the criminal law of England” that Blackstone discussed in his Commentaries. Id. at 715 (citing 4 W. Blackstone, Commentaries on the Laws of England 68 (1769)). Sosa recognized
that ATS liability is not limited to these paradigm torts,
however. Federal courts may hear claims “based on the
present-day law of nations” if those claims “rest on a norm
of international character accepted by the civilized world
and defined with a specificity comparable to the features
of the 18th-century paradigms [this Court has] recognized.”
Id. at 725. In Jesner v. Arab Bank, PLC, 584 U.S. 241
(2018), the Court reaffirmed Sosa’s holding that “courts
may recognize a common-law cause of action for claims
8
based on the present-day law of nations, in addition to the
‘historical paradigms familiar when § 1350 was enacted.’ ”
584 U.S. at 256 (quoting Sosa, 542 U.S. at 732)).
Consistent with the plain language of the ATS, Sosa
makes clear that whether a claim is actionable under the
statute depends on customary international law. Sosa
noted that, at the time of the statute’s enactment, the ATS
“enabled federal courts to hear claims in a very limited
category defined by the law of nations and recognized
at common law.” 542 U.S. at 712 (emphasis added). It
repeatedly described the claims actionable under the ATS
as violations of “international norm[s].” See, e.g., id. at 730
(“international norm intended to protect individuals”);
ibid. (“enforceable international norms”); id. at 732 (“violations of any international law norm”); see also id. at 733
(referring to “the current state of international law”). And
when addressing the ATS’s applicability to private actors,
Sosa looked to “whether international law extends the
scope of liability for a violation of a given norm to the perpetrator being sued.” Id. at 732 n.20 (emphasis added). As
the cases Sosa cited in footnote 20 make clear, Sosa examined that question because international law requires state
action for some human rights violations (e.g., torture) but
not for others (e.g., genocide). See ibid.
The point is that whether a claim is actionable under
Sosa turns on the content of customary international law,
not U.S. domestic law. The norm must be both “accepted
by the civilized world” and “defined with a specificity comparable” to the international law torts familiar to the First
Congress. Sosa, 542 U.S. at 725.
9
II. CUSTOMARY INTERNATIONAL LAW’S PROHIBITION
AGAINST AIDING AND ABETTING HUMAN RIGHTS VIOLATIONS MEETS THE SOSA STANDARD
A review of customary international law demonstrates
that the prohibition against aiding and abetting international law violations meets the Sosa standard. It is both
“accepted by the civilized world” and “defined with a specificity comparable” to the paradigmatic torts this Court
has recognized. Sosa, 542 U.S. at 725. The prohibition on
aiding and abetting is “a norm that is specific, universal,
and obligatory.” Jesner, 584 U.S. at 258 (plurality) (quoting
Sosa, 542 U.S. at 732).2
A. The Prohibition Against Aiding and Abetting Is
Generally Accepted
In customary international law, “the development [of
aiding-and-abetting liability] began in earnest with the
work of the International Military Tribunals after the Second World War.” Oona A. Hathaway, Alexandra Francis,
Aaron Haviland, Srinath Reddy Kethireddy & Alyssa
Yamamoto, Aiding and Abetting in International Criminal Law, 104 Cornell L. Rev. 1593, 1601 (2019). After the
war, the victorious nations promulgated the London Charter establishing the International Military Tribunal at
Nuremberg to try the major war criminals of the European
Axis. See Agreement for the Prosecution and Punishment
of the Major War Criminals of the European Axis and
Charter of the International Military Tribunal (“London
Charter”), Aug. 8, 1945, 59 Stat. 1544, 82 U.N.T.S. 279.
The drafters of the London Charter found it insufficient
simply to punish those who directly perpetrated the heiAiding-and-abetting liability was well established when the ATS was
enacted. See Resp. Br. 13-15. Amici focus on “the present-day law of
nations.” Sosa, 542 U.S. at 725.
2
10
nous violations of international law at issue. Instead, they
extended liability for crimes against peace, war crimes,
and crimes against humanity to “[l]eaders, organizers, instigators and accomplices participating in the formulation
or execution of a common plan or conspiracy to commit
any of the foregoing crimes.” London Charter art. 6 (emphasis added). Control Council Law No. 10, under which
the Allied powers conducted additional trials, similarly
provided that a person would be deemed to have committed
a crime under the London Charter if he “was an accessory
to the commission of any such crime or ordered or abetted
the same.” Control Council Law No. 10 art. II(2)(b), 1
Enactments and Approved Papers of the Control Council
and Coordinating Committee: Allied Control Authority,
Germany–1945, at 309, 311 (1946) (emphasis added). Several defendants were convicted at Nuremberg of aiding
and abetting under these standards. See, e.g., The Zyklon
B Case (Trial of Bruno Tesch and Two Others), 1 Law
Reports of Trials of War Criminals 93 (1947); The Einsatzgruppen Case (Trial of Otto Ohlendorf and Others), 4
Trials of War Criminals Before the Nuernberg Military
Tribunals Under Control Council Law No. 10, at 411
(1952); United States v. Flick, 6 Trials of War Criminals
Before the Nuernberg Military Tribunals Under Control
Council Law No. 10, at 1187 (1952).
Those prosecutions were neither making new law nor
meting out ex post facto punishments. Consistent with the
international law principle of legality that prohibits creating
new crimes after the fact (nullum crimen sine lege), the
London Charter, Control Council Law No. 10, and the
prosecutions conducted under them reflect the international community’s understanding that customary international law prohibited aiding and abetting international law
violations when the charged conduct occurred. The Inter-
11
national Military Tribunal said as much: “The [London]
Charter is not an arbitrary exercise of power on the part
of the victorious Nations, but * * * the expression of international law existing at the time of its creation.” Judgment of the International Military Tribunal, 1 Trial of the
Major War Criminals Before the International Military
Tribunal 171, 218 (1947). And in 1950, the International
Law Commission summarized the customary international law applied at Nuremberg as including the principle
that “[c]omplicity in the commission of a crime against
peace, a war crime, or a crime against humanity * * * is a
crime under international law.” Principles of International Law Recognized in the Charter of the Nürnberg
Tribunal and in the Judgment of the Tribunal, Principle
VII, Report of the International Law Commission on the
Work of Its Second Session, U.N. Doc. A/1316 (1950).
International agreements and international legal tribunals since Nuremberg have consistently reaffirmed that
aiding and abetting a violation of international law is itself
a violation of customary international law.
In 1993, the U.N. Security Council established the International Criminal Tribunal for the former Yugoslavia
(“ICTY”) to prosecute violations of customary international law. See Security Council Resolution 827 (May 25,
1993). Defining the crimes over which the Tribunal has
jurisdiction, the ICTY Statute provides: “A person who
planned, instigated, ordered, committed or otherwise aided
and abetted in the planning, preparation or execution of a
crime referred to in articles 2 to 5 of the present Statute,
shall be individually responsible for the crime.” Statute of
the International Criminal Tribunal for the Former Yugoslavia art. 7(1), in Report of the Secretary General Pursuant to Paragraph 2 of Security Council Resolution 808
(“ICTY Report”), U.N. Doc. S/25704 (May 3, 1993) (em-
12
phasis added); see also Updated Statute of the International Criminal Tribunal for the Former Yugoslavia art.
7(1) (July 7, 2009) (same).
That provision reflected customary international law at
the time. Like the Nuremberg Tribunals, the ICTY was
specifically required to “apply rules of international humanitarian law which are beyond any doubt part of customary law.” ICTY Report ¶ 34; see also Prosecutor v.
Blaškiþ, IT-95-14-A, Appeals Judgment, ¶ 141 (ICTY 2004)
(“[T]he Tribunal may enter convictions only where it is
satisfied that the offence is proscribed under customary
international law at the time of its commission.”). The
ICTY convicted many defendants of aiding and abetting.
See, e.g., Prosecutor v. Popoviþ, IT-05-88-A, Appeals Judgment (ICTY 2015); Prosecutor v. Lukiþ, IT-98-32/1-A, Appeals Judgment (ICTY 2012); Prosecutor v. Mrkšiþ, IT95-13/1-A, Appeals Judgment (ICTY 2009); Prosecutor v.
Blagojeviþ, IT-02-60-A, Appeals Judgment (ICTY 2007);
Prosecutor v. Simiþ, IT-95-9-A, Appeals Judgment (ICTY
2006); Prosecutor v. KvoĀka, IT-98-30/1-A, Appeals Judgment (ICTY 2005); Prosecutor v. Vasiljeviþ, IT-98-32-A,
Appeals Judgment (ICTY 2004); Prosecutor v. Furundžija, IT-95-17/1, Trial Judgment (ICTY 1998).
The International Criminal Tribunal for Rwanda
(“ICTR”), established in 1994, was likewise created to
prosecute crimes under existing customary international
law. See Security Council Resolution 955 (Nov. 8, 1994).
The ICTR Statute contains language identical to the ICTY
Statute on aiding and abetting. Statute of the International Tribunal for Rwanda art. 6(1) (Nov. 8, 1994), in
Security Council Resolution 955 annex (“A person who
planned, instigated, ordered, committed or otherwise
aided and abetted in the planning, preparation or execution of a crime referred to in articles 2 to 4 of the present
13
Statute, shall be individually responsible for the crime.”
(emphasis added)). The ICTR likewise convicted many
defendants of aiding and abetting international law violations, primarily genocide. See, e.g., Prosecutor v. Nyiramasuhuko, ICTR-98-42-A, Appeals Judgment (ICTR 2015);
Prosecutor v. Ntawukulilyayo, ICTR-05-82-A, Appeals
Judgment (ICTR 2011); Prosecutor v. Rukundo, ICTR2001-70-A, Appeals Judgment (ICTR 2010); Prosecutor v.
Karera, ICTR-01-74-A, Appeals Judgment (ICTR 2009);
Prosecutor v. Nahimana, ICTR-99-52-A, Appeals Judgment (ICTR 2007); Prosecutor v. Muhimana, ICTR-951B-A, Appeals Judgment (ICTR 2007); Prosecutor v. Ntagerura, ICTR-99-46-A, Appeals Judgment (ICTR 2006);
Prosecutor v. Ntakirutimana, ICTR-96-10-A & ICTR-9617-A, Appeals Judgment (ICTR 2004); Prosecutor v. Kayishema, ICTR-95-1-A, Appeals Judgment (ICTR 2001).3
Liability for complicity, which includes aiding and abetting, is also recognized in international conventions codifying established norms such as torture and genocide.
The Convention Against Torture provides in Article 4(1):
“Each State Party shall ensure that all acts of torture are
offences under its criminal law. The same shall apply to
A database of aiding-and-abetting cases decided by the ICTY, ICTR,
and other international criminal tribunals is available at Aiding and
Abetting in International Criminal Law, Yale Law School Lillian
Goldman Law Library Documents Collection Center, https://docu
ments.law.yale.edu/aiding-and-abetting-cases. Although the United
Nations later established other criminal tribunals for Sierra Leone,
Cambodia, and Lebanon, those tribunals apply varying combinations
of international and domestic law, rather than purely customary international law, and thus “should be approached with caution.” Hathaway et al., supra, at 1624. The Rome Statute of the International
Criminal Court art. 25(3)(c), July 17, 1998, 2187 U.N.T.S. 90, provides
for aiding-and-abetting liability, but it too was not intended to codify
customary international law. See Section II.B, infra.
3
14
an attempt to commit torture and to an act by any person
which constitutes complicity or participation in torture.”
Convention Against Torture and Other Cruel, Inhuman or
Degrading Treatment or Punishment art. 4(1), Dec. 10,
1984, S. Treaty Doc. No. 100-20, 1465 U.N.T.S. 85 (emphasis added). Article III of the Genocide Convention similarly provides that “[c]omplicity in genocide” is “punishable.” Convention on the Prevention and Punishment of
the Crime of Genocide art. III, Dec. 9, 1948, 102 Stat. 3045,
78 U.N.T.S. 277.4
In sum, international criminal tribunals from Nuremberg to the ICTY and ICTR have consistently proscribed
and punished aiding and abetting as a violation of customary international law. Modern human rights treaties such
as the Convention Against Torture and the Genocide Convention confirm that norm by recognizing liability for complicity. There is thus no doubt today that the prohibition
against aiding and abetting human rights violations is a
generally accepted norm of customary international law
“accepted by the civilized world.” Sosa, 542 U.S. at 725.
The International Court of Justice has noted that “the principles underlying the [Genocide] Convention are principles which are recognized by civilized nations as binding on States, even without any conventional obligation.” Reservations to the Convention on Prevention
and Punishment of the Crime of Genocide, Advisory Opinion, 1951
I.C.J. 15, 23 (May 28, 1951). And the ICTY Appellate Chamber has
stated that “[t]he definition of the crime of torture, as set out in the
[Convention Against Torture], may be considered to reflect international law.” Prosecutor v. Kunarac, IT-96-23 & IT-96-23/1-A, Appeals
Judgment, ¶ 146 (ICTY 2002). If anything, the Torture Convention is
narrower in certain respects than customary international law. See
id. ¶ 148 (Convention’s “public official” requirement more restrictive
than customary international law).
4
15
B. The Prohibition Against Aiding and Abetting Is
Specifically Defined
To meet the Sosa standard, a customary international
law norm must also be specifically defined. Amicus WLF
argues that the prohibition against aiding and abetting is
not specifically defined because international law sources
“cannot agree on the mens rea and actus reus required for
a conviction.” WLF Br. 6. This is incorrect.5
While not defined in the instruments establishing international criminal tribunals, the actus reus and mens rea
requirements for aiding-and-abetting liability under customary international law have been repeatedly articulated
in judicial decisions applying the prohibition. Those decisions clearly establish two requirements: (1) assistance that
has a substantial effect on the perpetration of the principal’s offense (the actus reus); and (2) knowledge that the
acts assist the commission of the offense (the mens rea).
1. Actus Reus
The Appeals Chamber of the ICTY has held that “under
customary international law, the actus reus of aiding and
abetting ‘consists of practical assistance, encouragement,
or moral support which has a substantial effect on the perpetration of the crime.’ ” Prosecutor v. Šainoviþ, IT-05-87A, Appeals Judgment, ¶ 1649 (ICTY 2014) (quoting Prosecutor v. Blaškiþ, IT-95-14-A, Appeals Judgment, ¶ 46 (ICTY
2004)); see also Popoviþ, IT-05-88-A, Appeals Judgment,
¶ 1732; Prosecutor v. Stanišiþ, IT-03-69-A, Appeals JudgPetitioners sought certiorari on the substantive mens rea standard
for aiding-and-abetting liability, but this Court did not grant certiorari
on that question. See Pet. i; Order (Jan. 9, 2026). Amici therefore
address the standards for aiding-and-abetting liability under customary international law for the limited purpose of showing that the prohibition against aiding and abetting is defined with sufficient specificity to meet the Sosa standard.
5
16
ment, ¶ 104 (ICTY 2015); Lukiþ, IT-98-32/1-A, Appeals
Judgment, ¶ 422; Prosecutor v. Aleksovski, IT-95-14/1-A,
Appeals Judgment, ¶ 162 (ICTY 2000); Furundžija, IT-9517/1-T, Trial Judgment, ¶ 249 (ICTY 1998).
The ICTR has adopted an identical rule. See Nyiramasuhuko, ICTR-98-42-A, Appeals Judgment, ¶ 1955; Prosecutor v. Ndahimana, ICTR-01-68-A, Appeals Judgment,
¶ 147 (ICTR 2013); Ntawukulilyayo, ICTR-05-82-A, Appeals Judgment, ¶ 214; Rukundo, ICTR-2001-70-A, Appeals Judgment, ¶ 52; Prosecutor v. Seromba, ICTR-0166-A, Appeals Judgment, ¶ 139 (ICTR 2008); Muhimana,
ICTR-95-1B-A, Appeals Judgment, ¶ 189; Ntagerura,
ICTR-99-46-A, Appeals Judgment, ¶ 370; Prosecutor v.
Ntakirutimana, ICTR-96-10-A & ICTR-96-17-A, Appeals
Judgment, ¶ 530 (ICTR 2004).
That standard dates back to the Nuremberg tribunals.
See Furundžija, IT-95-17/1-T, Trial Judgment, ¶¶ 217226, 233-234 (tracing use of the “substantial effect” standard at Nuremberg). In the Einsatzgruppen Case, for example, the U.S. Military Tribunal distinguished between
defendants who could affect the course of events and those
who could not. See The Einsatzgruppen Case, 4 Trials of
War Criminals Before the Nuernberg Military Tribunals
Under Control Council Law No. 10, at 411 (1952). Thus,
the Tribunal acquitted one defendant because his “low
rank [did not] place him automatically into a position
where his lack of objection in any way contributed to the
success of any executive operation,” and it held that another defendant “cannot be found guilty as an accessory”
because he was not “in a position to protest against the
illegal actions of others.” Id. at 581, 585. Similarly, in the
Zyklon B Case, the British Military Tribunal convicted
two individuals for supplying poison gas for use in concentration camps, but acquitted a subordinate because, “[i]f
17
he were not in such a position [either to influence the
transfer of gas to Auschwitz or to prevent it], no knowledge of the use to which the gas was being put could make
him guilty.” The Zyklon B Case, 1 Law Reports of Trials
of War Criminals 93, 93, 102 (1947).
The decisions of the ICTY and ICTR have defined the
actus reus standard with even greater specificity. They
have held, for example, that but-for causation is not required. See, e.g., Popoviþ, IT-05-88-A, Appeals Judgment,
¶ 1740; Simiþ, IT-95-9-A, Appeals Judgment, ¶ 85; Nyiramasuhuko, ICTR-98-42-A, Appeals Judgment, ¶ 1955;
Prosecutor v. Kalimanzira, ICTR-05-88-A, Appeals Judgment, ¶ 86 (ICTR 2010). They have clarified when the conduct in question must have occurred. See, e.g., Lukiþ, IT98-32/1-A, Appeals Judgment, ¶ 425; Kalimanzira, ICTR05-88-A, Appeals Judgment, ¶ 87 n.238. They have explained when omissions may constitute the actus reus.
See, e.g., Popoviþ, IT-05-88-A, Appeals Judgment, ¶ 1740;
Mrkšiþ, IT-95-13/1-A, Appeals Judgment, ¶¶ 146-152;
Ntagerura, ICTR-99-46-A, Appeals Judgment, ¶ 370. And
they have clarified that the acts of aiding and abetting
need not be directed toward a specific crime. See Šainoviþ, IT-05-87-A, Appeals Judgment, ¶ 1649; Nyiramasuhuko, ICTR-98-42-A, Appeals Judgment, ¶ 1955.
2. Mens Rea
The Appellate Chambers of the ICTY and ICTR have
likewise applied, without exception, the same mens rea
standard: “knowledge that [the defendant’s] acts assist
the commission of the offense.” Šainoviþ, IT-05-87-A, Appeals Judgment, ¶ 1649 (quoting Blaškiþ, IT-95-14-A, Appeals Judgment, ¶ 46); Nyiramasuhuko, ICTR-98-42-A,
Appeals Judgment, ¶ 1955 (quoting Šainoviþ, IT-05-87-A,
Appeals Judgment, ¶ 1649); see also Blagojeviþ, IT-02-60A, Appeals Judgment, ¶ 127; KvoĀka, IT-98-30/1-A, Ap-
18
peals Judgment, ¶ 89; Prosecutor v. Krnojelac, IT-97-25A, Appeals Judgment, ¶ 33 (ICTY 2003); Prosecutor v.
Tadiþ, IT-94-1-A, Appeals Judgment, ¶ 229 (ICTY 1999);
Furundžija, IT-95-17/1-T, Trial Judgment, ¶ 249; Ndahimana, ICTR-01-68-A, Appeals Judgment, ¶157; Ntawukulilyayo, ICTR-05-82-A, Appeals Judgment, ¶ 222; Rukundo, ICTR-2001-70-A, Appeals Judgment, ¶ 53; Muhimana,
ICTR-95-1B-A, Appeals Judgment, ¶ 189; Ntakirutimana,
ICTR-96-10-A & ICTR-96-17-A, Appeals Judgment, ¶ 530.
“Knowledge” was also the mens rea standard applied
by the international military tribunals at Nuremberg. In
the Einsatzgruppen Case, the tribunal noted that a defendant who turned over lists of Communist party members “served as an accessory” to their subsequent executions because he “was aware that the people listed would
be executed when found.” The Einsatzgruppen Case, 4
Trials of War Criminals Before the Nuernberg Military
Tribunals Under Control Council Law No. 10, at 569
(1952) (emphasis added); see also The Zyklon B Case, 1
Law Reports of Trials of War Criminals 93 (1947) (convicting defendants who “suppl[ied] poison gas used for the
extermination of allied nationals interned in concentration
camps well knowing that the said gas was to be so used.”
(emphasis added)); I.G. Farben Case, 8 Trials of War
Criminals Before the Nuernberg Military Tribunals Under
Control Council Law No. 10, at 1081, 1169 (1952) (acquitting
corporate executives who did not have “any significant
knowledge” that “an improper use was being made of
[Zyklon B]”). It was a “settled legal principl[e]” even then
that “[o]ne who knowingly by his influence and money
contributes to the support [of crimes against humanity
and war crimes] must * * * be deemed to be, if not a principal, certainly an accessory to such crimes.” United
States v. Flick, 6 Trials of War Criminals Before the
19
Nuernberg Military Tribunals Under Control Council
Law No. 10, at 1187, 1217 (1952) (emphasis added).6
As with actus reus, the ICTY and ICTR decisions have
defined the mens rea requirement with even greater specificity. For instance, an aider and abettor “need not share
the intent of the principal perpetrator” but “must be
aware of such intent.” Popoviþ, IT-05-88-A, Appeals Judgment, ¶ 1794; see also Ndahimana, ICTR-01-68-A, Appeals Judgment, ¶ 157; Ntawukulilyayo, ICTR-05-82-A,
Appeals Judgment, ¶ 222. Thus, “[s]pecific intent crimes
such as genocide require that the aider and abettor must
know of the principal perpetrator’s specific intent.” Ndahimana, ICTR-01-68-A, Appeals Judgment, ¶ 157; see also
Rukundo, ICTR-2001-70-A, Appeals Judgment, ¶ 53; Kalimanzira, ICTR-05-88-A, Appeals Judgment, ¶ 86.
United States v. von Weizsaecker (The Ministries Case), 14 Trials of
War Criminals Before the Nuernberg Military Tribunals Under Control Council Law No. 10, at 314 (1952), is not to the contrary. Though
sometimes cited to support a requirement that the defendant act with
the purpose of facilitating the violation, see Presbyterian Church of
Sudan v. Talisman Energy, Inc., 582 F.3d 244, 259 (2d Cir. 2009), the
relevant portion of the Ministries Case was actually about actus reus,
not mens rea. In acquitting the banker Karl Rasche, the tribunal concluded that, although Rasche knew that a loan he made would be used
to “financ[e] enterprises which are employed in using labor in violation
of either national or international law,” merely making a loan does not
make the lender a “partner in [the] enterprise.” The Ministries Case,
14 Trials of War Criminals Before the Nuernberg Military Tribunals
Under Control Council Law No. 10, at 622 (1952). In other words, the
tribunal found a lack of actus reus rather than mens rea. Indeed, the
tribunal clearly articulated and applied a knowledge standard to other
defendants in the same case. See id. at 478 (“The question is whether
[Von Weizsaecker and Woermann] knew of the program and whether
in any substantial manner they aided, abetted, or implemented it.”);
id. at 620 (convicting banker who “knew that what was to be received
and disposed of was stolen property and loot taken from the inmates
of concentration camps”).
6
20
Although two Circuits have adopted a narrower “purpose” standard for aiding-and-abetting liability, they did
so based on authorities that by their terms do not reflect
customary international law. See Presbyterian Church of
Sudan v. Talisman Energy, Inc., 582 F.3d 244, 259 (2d
Cir. 2009); Aziz v. Alcolac, Inc., 658 F.3d 388, 400-401
(4th Cir. 2011). Neither those cases nor the authorities
they cite call into question that, under customary international law, the “knowledge” standard is well-defined and
universally accepted.
Both courts adopted the “purpose” standard from the
Rome Statute of the International Criminal Court (“Rome
Statute”), July 17, 1998, 2187 U.N.T.S. 90. See Talisman,
582 F.3d at 258-259; Aziz, 658 F.3d at 398-401; see also Pet.
App. 52a-58a. The Rome Statute extends criminal liability
to a person who, “[f]or the purpose of facilitating the commission of such a crime, aids, abets or otherwise assists in
its commission or its attempted commission, including
providing the means for its commission.” Rome Statute
art. 25(3)(c). But this provision of the Rome Statute does
not reflect customary international law. The lead negotiator for the United States, Ambassador David Scheffer,
told this Court in 2010 that “Article 25(3)(c) of the Rome
Statute was negotiated not to codify customary international law but to accommodate the numerous views of
common law and civil law experts about how, precisely, to
express the mens rea of the aider or abettor.” Scheffer
Br. in Presbyterian Church of Sudan v. Talisman Energy,
Inc., No. 09-1262, at 11 (May 19, 2010) (emphasis added).
Thus, “understanding the Rome Statute as an effort to
21
codify customary international law at the time it was
drafted is a mistake.” Hathaway et al., supra, at 1599.7
Relying on the Rome Statute to interpret the ATS disregards Sosa’s direction to consult customary international law. It also disregards the text of the ATS, which
refers to torts “in violation of the law of nations or a treaty
of the United States.” 28 U.S.C. § 1350 (emphasis added).
Because the United States is not a party to the Rome Statute, it cannot qualify as a treaty “of the United States.”
Any divergence in the standards for aiding-and-abetting liability merely reflects differences between tribunals
that are charged with applying customary international
law and those that are not. See Hathaway et al., supra, at
1610-1611, 1613-1617. Tribunals applying customary international law from Nuremberg onward have consistently
required (1) assistance that has a substantial effect on the
perpetration of the principal’s offense; and (2) knowledge
that the acts assist the commission of the offense. Customary international law thus defines the prohibition
against aiding and abetting international law violations
with all the specificity that Sosa requires.
III. INTERNATIONAL LAW ALLOWS THE UNITED STATES
TO IMPOSE CIVIL LIABILITY FOR AIDING AND ABETTING HUMAN RIGHTS VIOLATIONS
Amicus WLF acknowledges that aiding-and-abetting
liability “finds some support in international criminal tribunals,” but argues that “no source of international law
Several of the Rome Statute’s provisions distinguish its rules from
those of customary international law. See Rome Statute art. 10
(“Nothing in this Part shall be interpreted as limiting or prejudicing
in any way existing or developing rules of international law for purposes other than this Statute.”); id. art. 22(3) (“This article [on nullum
crimen sine lege] shall not affect the characterization of any conduct
as criminal under international law independently of this Statute.”).
7
22
* * * provides a civil remedy for any international crime.”
WLF Br. at 6-7 (emphasis original). That distinction between civil and criminal remedies misunderstands how
customary international law works.
Customary international law establishes substantive
norms of conduct but does not dictate how those norms are
enforced in national legal systems. See Eileen Denza, The
Relationship Between International and National Law,
in International Law 411, 411 (Malcolm D. Evans ed., 3d
ed. 2010) (“[I]nternational law does not itself prescribe
how it should be applied or enforced at the national
level.”); Louis Henkin, Foreign Affairs and the United
States Constitution 245 (2d ed. 1996) (“International law
itself * * * does not require any particular reaction to violations of law.”); Restatement (Third) of U.S. Foreign Relations Law § 111 cmt. h (1987) (“In the absence of special
agreement, it is ordinarily for the United States to decide
how it will carry out its international obligations.”). This
Court acknowledged that relationship between customary
international law and domestic law in Banco Nacional de
Cuba v. Sabbatino, 376 U.S. 398 (1964), noting that “the
public law of nations can hardly dictate to a country * * *
how to treat [a violation of international law] within its domestic borders.” Id. at 423. Different legal systems thus
can and do take different approaches to implementing international law norms. See, e.g., Chimène I. Keitner, Conceptualizing Complicity in Alien Tort Cases, 60 Hastings
L.J. 61, 85 (2008) (“The sharp distinction between civil and
criminal proceedings and penalties is a feature identified
with modern common law systems, not the international
system as a whole.”).
The consistent practice described in Part II clearly establishes that the prohibition against aiding and abetting
international law violations is a generally accepted and
23
clearly defined norm of customary international law.
Although that norm has generally been enforced internationally by criminal tribunals, that practice does not foreclose countries like the United States from imposing civil
liability domestically for violations.8
That is what the First Congress did when it created
civil liability for torts “in violation of the law of nations” in
the ATS. 28 U.S.C. § 1350. The three paradigmatic offenses it had in mind—violations of safe conducts, infringement of the rights of ambassadors, and piracy—
were all offenses “addressed by the criminal law of England.” Sosa, 542 U.S. at 715 (citing 4 W. Blackstone, Commentaries on the Laws of England 68 (1769)) (emphasis
added). Nevertheless, Congress chose to open the doors
of the federal courts to civil claims for the same offenses.
* * * * *
The statutes of some international criminal tribunals do provide for
restitution to victims. See, e.g., ICTY Statute art. 24(3); ICTR Statute
art. 23(3). Civil aiding-and-abetting liability also finds a counterpart
in the customary international law of state responsibility. Article 16
of the International Law Commission’s Draft Articles on State Responsibility provides: “A State which aids or assists another State in
the commission of an internationally wrongful act by the latter is
internationally responsible for doing so if: (a) that State does so with
knowledge of the circumstances of the internationally wrongful act;
and (b) the act would be internationally wrongful if committed by that
State.” Int’l Law Comm’n, Draft Articles on Responsibility of States
for Internationally Wrongful Acts, with Commentaries, art. 16, Report
of the International Law Commission on the Work of Its Fifty-Third
Session, U.N. Doc. A/56/10, at 65 (2001). The International Court of
Justice has referred to Article 16 as reflecting a rule of customary
international law. See Case Concerning Application of the Convention on the Prevention and Punishment of the Crime of Genocide
(Bosnia v. Serbia), 2007 I.C.J. 43, ¶ 420 (Feb. 26, 2007).
8
24
Under this Court’s decision in Sosa, whether the prohibition on aiding and abetting is the kind of norm actionable
under the ATS is determined by customary international
law. Since at least the 1940s, customary international law
has prohibited aiding and abetting violations of international law. That norm is both generally accepted and
specifically defined. And the fact that the international
community has chosen to enforce that norm through international criminal tribunals does not preclude countries
from imposing civil liability for the same violations, as the
United States has done in the ATS.
CONCLUSION
The court of appeals’ judgment should be affirmed.
Respectfully submitted.
ROBERT K. KRY
Counsel of Record
JACKSON A. MYERS
MOLOLAMKEN LLP
The Watergate, Suite 500
600 New Hampshire Ave., N.W.
Washington, D.C. 20037
(202) 556-2000
rkry@mololamken.com
Counsel for Amici Curiae
MARCH 2026
This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.