Under the Alien Tort Claims Act.
 The Alien Tort Claims Act confers upon the federal district courts original
jurisdiction of any civil action by an alien for a tort only, committed
in violation of the law of nations. 28 U.S.C. § 1350.12 We have held that the ATCA also provides a cause of action, as long
as plaintiffs . . . allege a violation of specific, universal,
and obligatory international norms as part of [their] ATCA claim. Papa v. United States, 281 F.3d 1004, 1013 (9th Cir. 2002) (quoting In re Estate of Ferdinand E. Marcos, Human Rights Litig., 25
F.3d 1467, 1475 (9th Cir. 1994) (Marcos II)). See
also Marcos II, 25 F.3d at 1474-75. Plaintiffs allege that Unocals
conduct gave rise to ATCA liability for the forced labor, murder, rape,
and torture inflicted on them by the Myanmar Military.13
District Court granted Unocals motion for summary judgment on
Plaintiffs ATCA claims. We review a grant of summary judgment de novo. See Lopez v. Smith, 203 F.3d 1122, 1131 (9th Cir. 2000)
(en banc). We must determine whether, viewing the evidence in the light
most favorable to the nonmoving party, there are any genuine issues
of material fact and whether the district court correctly applied the
relevant substantive law. See id.
 One threshold question in any ATCA case is whether the alleged
tort is a violation of the law of nations. We have recognized that torture,
murder, and slavery are jus cogens violations and, thus, violations
of the law of nations.14 See United
States v. Matta-Ballesteros, 71 F.3d 754, 764 n.5 (9th Cir. 1995).
Rape can be a form of torture. See Farmer v. Brennan, 511 U.S.
825, 852, 854 (1994) (Blackmun, J., concurring) (describing brutal prison
rape as the equivalent of and nothing less than torture); Kadic v. Karadzic, 70 F.3d 232, 242 (2d Cir. 1995) (describing
allegations of murder, rape, forced impregnation, and other
forms of torture (emphasis added)); In re Extradition of
Suarez-Mason, 894 F. Supp. 676, 682 (N.D. Cal. 1988) (stating that
shock sessions were interspersed with rapes and other forms
of torture (emphasis added)); see also generally Evelyn
Mary Aswad, Torture by Means of Rape, 84 Geo. L.J. 1913 (1996).
Moreover, forced labor is so widely condemned that it has achieved the
status of a jus cogens violation. See, e.g., Universal
Declaration of Human Rights, G.A. Res. 217(A)III (1948) (banning forced
labor); 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, art. 6, 82 U.N.T.S. 280 (making forced labor
a war crime). Accordingly, all torts alleged in the present case are
jus cogens violations and, thereby, violations of the law of nations.15
 Another threshold question in any ATCA case against a private party,
such as Unocal, is whether the alleged tort requires the private party
to engage in state action for ATCA liability to attach, and if so, whether
the private party in fact engaged in state action. In his concurrence
in Tel-Oren v. Libyan Arab Republic, 726 F.2d 774 (D.C. Cir.
1984), Judge Edwards observed that while most crimes require state action
for ATCA liability to attach, there are a handful of crimes,
including slave trading, to which the law of nations attributes individual liability, such that state action is not required.
Id. at 794-95 (Edwards, J., concurring) (emphasis added).16 More recently, the Second Circuit adopted and extended this approach
in Kadic. The Second Circuit first noted that genocide and war
crimes like slave trading do not require state action
for ATCA liability to attach. See 70 F.3d at 242-243. The Second
Circuit went on to state that although acts of rape, torture,
and summary execution, like most crimes, are proscribed
by international law only when committed by state officials or under
color of law to the extent that they were committed in isolation,
these crimes are actionable under the Alien Tort [Claims] Act,
without regard to state action, to the extent that they were committed in pursuit of genocide or war crimes. Id. at 243-44
(emphasis added). Thus, under Kadic, even crimes like rape, torture,
and summary execution, which by themselves require state action for
ATCA liability to attach, do not require state action when committed
in furtherance of other crimes like slave trading, genocide or war crimes,
which by themselves do not require state action for ATCA liability to
attach. We agree with this view and apply it below to Plaintiffs
various ATCA claims.
2. Forced Labor
Forced labor is a modern variant of slavery to which the law of nations
attributes individual liability such that state action is not required.
case law strongly supports the conclusion that forced labor is a modern
variant of slavery. Accordingly, forced labor, like traditional variants
of slave trading, is among the handful of crimes . . . to which
the law of nations attributes individual liability, such
that state action is not required. Id. at 794-95 (Edwards, J., concurring). See supra section II.A.1.
have included forced labor in the definition of the term slavery
in the context of the Thirteenth Amendment.17 The Supreme Court has said that [t]he undoubted aim of the Thirteenth
Amendment . . . was not merely to end slavery but to maintain a system
of completely free and voluntary labor throughout the United
States. Pollock v. Williams, 322 U.S. 4, 17 (1944) (emphasis
added).18 Accordingly, [i]t has
been held that forced labor of certain individuals amounts to involuntary
servitude and therefore is violative of the thirteenth amendment. Weidenfeller v. Kidulis, 380 F. Supp. 445, 450 (E.D. Wis. 1974)
(citing Stone v. City of Paducah, 86 S.W. 531, 533 (Ky. 1905)).
inclusion of forced labor in the definition of the term slavery
is not confined to the Thirteenth Amendment but extends, for example,
to 18 U.S.C. § 1583. 18 U.S.C. § 1583 was introduced in 1866
to prevent the kidnaping of former slaves to countries which still permitted
slavery.19 The Fourth Circuit has said
that [n]otwithstanding this limited purpose, the statute should
be read as expressing the broad and sweeping intention of Congress during
the Reconstruction period to stamp out the vestiges of the old regime
of slavery and to prevent the reappearance of forced labor in whatever
new form it might take. United States v. Booker, 655
F.2d 562, 565 (4th Cir. 1981) (emphasis added).
In World War II Era Japanese Forced Labor Litig., 164 F. Supp. 2d
1160, (N.D. Cal. 2001), the District Court for the Northern District
of California recently implicitly included forced labor in the definition
of the term slavery for purposes of the ATCA. There, the
district court concluded that [g]iven the Ninth Circuits
comment in Matta-Ballesteros, 71 F.3d at 764 n.5, that slavery
constitutes a violation of jus cogens, this court is inclined
to agree with the [District Court for the District of New Jerseys]
conclusion [in Iwanowa v. Ford Motor Co., 67 F. Supp. 2d 424
(D.N.J. 1999)] that forced labor violates the law of nations. Id. at 1179.
 In light of these authorities, we conclude that forced labor is a modern
variant of slavery that, like traditional variants of slave trading,
does not require state action to give rise to liability under the ATCA.
Unocal may be liable under the ATCA for aiding and abetting the Myanmar
Military in subjecting Plaintiffs to forced labor.
argue that Unocal aided and abetted the Myanmar Military in subjecting
them to forced labor. We hold that the standard for aiding and abetting
under the ATCA is, as discussed below, knowing practical assistance
or encouragement that has a substantial effect on the perpetration of
the crime. We further hold that a reasonable factfinder could find that
Unocals conduct met this standard.20
District Court found that [t]he evidence . . . suggest[s] that
Unocal knew that forced labor was being utilized and that the Joint
Venturers benefitted from the practice. Doe/Roe II, 110
F. Supp. 2d at 1310. The District Court nevertheless held that Unocal
could not be liable under the ATCA for forced labor because Unocals
conduct did not rise to the level of active participation
in the forced labor. Id. The District Court incorrectly borrowed
the active participation standard for liability from war
crimes cases before Nuremberg Military Tribunals involving the role
of German industrialists in the Nazi forced labor program during the
Second World War. The Military Tribunals applied the active participation
standard in these cases only to overcome the defendants necessity
defense.21 In the present case,
Unocal did not invoke and could not have invoked the necessity
defense. The District Court therefore erred when it applied the active
participation standard here.22
however agree with the District Court that in the present case, we should
apply international law as developed in the decisions by international
criminal tribunals such as the Nuremberg Military Tribunals for the
applicable substantive law. The law of nations may be ascertained
by consulting the works of jurists, writing professedly on public law;
or by the general usage and practice of nations; or by judicial decisions
recognizing and enforcing that law. Filartiga v.
Pena-Irala, 630 F.2d 876, 880 (2d Cir. 1980) (quoting United
States v. Smith, 18 U.S. (5 Wheat.) 153, 160-61 (1820)) (emphasis
added). It is well settled that the law of nations is part of
federal common law. Marcos I, 978 F.2d at 502.
The law of nations is the law of international relations,
embracing not only nations but also . . . individuals (such as those
who invoke their human rights or commit war crimes). Blacks
Law Dictionary 822 (7th ed. 1999).
Plaintiffs ATCA claims are timely under the ten-year statute of
limitations we recently adopted for such claims. See Papa, 281
F.3d at 1011-13.
14. Jus cogens norms are norms of international law that are binding
on nations even if they do not agree to them. See Siderman de Blake
v. Republic of Argentina, 965 F.2d 699, 714-15 (9th Cir. 1992).
We stress that although a jus cogens violation is, by definition,
a violation of specific, universal, and obligatory
international norms that is actionable under the ATCA, any violation of specific, universal, and obligatory international
norms jus cogens or not is actionable under
the ATCA. Papa, 281 F.3d at 1013 (quoting Marcos II, 25
F.3d at 1475). Thus, a jus cogens violation is sufficient, but
not necessary, to state a claim under the ATCA.
Our statement in In re Estate of Ferdinand E. Marcos Human Rights
Litig., 978 F.2d 493, 501-02 (9th Cir. 1992) (Marcos I),
that [o]nly individuals who have acted under official authority
or under color of such authority may violate international law,
must be read like Judge Edwards concurrence in Tel-Oren,
on which this statement exclusively relied. Marcos I, like Tel-Oren,
involved torture, a crime for which there is no purely private liability
under international law. See Tel-Oren, 726 F.2d at 794-95 (Edwards,
J., concurring); Kadic, 70 F.3d at 243.
The Thirteenth Amendment provides in part that [n]either slavery
nor involuntary servitude . . . shall exist within the United States.
U.S. CONST. amend. XIII, § 1. See also Tobias Barrington, The
Thirteenth Amendment and Slavery in the Global Economy, 102 Colum.
L. Rev. 973 (2002), for the proposition that the knowing use of
slave labor by U.S. based entities in their foreign operations constitutes
the presence of slavery within the United States, as that
term is used in the Thirteenth Amendment, id. at 978, and
that [i]f the allegations against it are true, then Unocals
participation in the Burma project makes out a strong case for a Thirteenth
Amendment violation, id. at 1034.
The fact that the Thirteenth Amendment reaches private action, see
Jones v. Alfred H. Mayer Co., 392 U.S. 409, 438-39 (1968), in turn
supports the view that forced labor by private actors gives rise to
liability under the ATCA.
The statute provides that anybody who kidnaps any other person, or induces
such other person to go anywhere, with the intent that such other person
be sold into involuntary servitude or held as a slave, shall be fined
or imprisoned as specified. See 18 U.S.C. § 1581.
Plaintiffs also argue that Unocal is liable for the conduct by the Myanmar
Military under joint venture, agency, negligence, and recklessness theories.
The District Court did not address any of Plaintiffs alternative
theories. Because we reject the District Courts general reasons
for holding that Unocal could not be liable under international law,
and because we hold that Unocal may be liable under at least one of
Plaintiffs theories, i.e., aiding and abetting in violation of
international law, we do not need to address Plaintiffs other
theories, i.e., joint venture, agency, negligence, and recklessness.
Joint venture, agency, negligence, and recklessness may, like aiding
and abetting, be viable theories on the specific facts of this ATCA
case. Moreover, on the facts of other ATCA cases, joint venture, agency,
negligence, or recklessness may in fact be more appropriate theories
than aiding and abetting.
The Military Tribunal in one of these case defined the necessity defense
as follows: Necessity is a defense when it is shown that the act
charged was done to avoid an evil both serious and irreparable; that
there was no other adequate means of escape; and that the remedy was
not disproportionate to the evil. United States v. Krupp,
9 Trials of War Criminals Before the Nuremberg Military Tribunals Under
Control Council Law No. 10, 1436 (1950) [Krupp]).
(quoting 1 Whartons Criminal Law 177 (12th ed. 1932)).
A reasonable factfinder could moreover conclude that Unocals conduct
met the active participation standard erroneously applied
by the District Court. For example, Unocal Representative Robinson stated
that [o]ur assertion that [the Myanmar Military] has not expanded
and amplified its usual methods around the pipeline on our behalf may
not withstand much scrutiny. Robinson is furthermore reported
to have stated that Total/Unocal uses [photos, maps, and surveys]
to show the military where they need helipads built and facilities secured.
In addition, Unocal President Imle stated that [i]f forced labor
goes hand in glove with the military yes there will be more forced labor
as the result of the Myanmar Military protecting the pipeline. Unocal
thus resembles the defendants in Krupp, who well knew that
any expansion [of their business] would require the employment of forced
labor, 9 Trials at 1442, and the defendants in United States
v. Flick, 6 Trials of War Criminals Before the Nuremberg Military
Tribunals Under Control Council Law No. 10 (1952), who sought to increase
their production quota and thus their forced labor allocation, id. at 1198, 1202.