B. Customary International Law

Customary international law results when there’s a general and consistent practice of states following laws from a sense of legal obligation (opinio juris). The assessment of state practice is an objective one. The significance of a particular act as indicia of custom varies depending on its context and may also be subject matter specific. For example, a presidential statement would be more important than a military commander’s unless in the context of the law of war. This is one form of aperture. Treaties may be strong empirical evidence of state practice, especially if they purport to codify customary international law. Evidence of state practice may be divined from diplomatic contacts, public statements, legislative and executive acts, military decisions, treaties, and decisions of courts and international organization. These areas tend to be married to political processes, especially in democratic countries. While state practice should be uniform, extensive, and representative, the political context surrounding certain issues can lead one state’s practice to carry more weight than the other. Further, political reasoning may lead one state to act as a persistent objector to a developing norm of customary international law, which would relieve that state from abiding by the rule—a practice that was embraced by the United States at the end of the twentieth century.5 However, rules that are already crystallized into customary law are binding upon all States of the international community—a State is not allowed to opt out unilaterally.6 The assessment of opinio juris is a subjective one. The principle idea embedded in this requirement is to distinguish customary international law from everyday customs of states followed out of formality, courtesy, convenience, or habit.

C. Soft Law

Since 1945, the significance of “general principles of law” recognized by civilian nations referenced in the ICJ Statute has decreased. Soft law has risen in prominence as a source of international law. Soft law refers to instruments which are neither strictly binding norms of law, nor completely irrelevant political maxims. They operate in a grey zone between law and politics.7 It is defined as declared norms of conduct understood as legally nonbinding by those accepting the norms, emanating from regulatory activities that are non-binding although states comply without a core treaty. Soft law has developed because the international system has become more interdependent and states desire informal agreements that do not require costly negotiations on binding laws in rapidly developing domains. Even more so than customary international law, the reasoning for states to participate in the creation of soft law is impacted by political processes at play among states. Soft law may reflect or help form a standard of appropriate conduct and induce significant and actual conformity with that standard even in the absence of applicable binding custom or treaty, and may eventually give rise to a customary international law norm.

III. Case Studies

A. Evolution of Crimes Against Humanities

The phrase “crimes against humanity” was coined by U.S. Supreme Court Justice Robert Jackson during deliberations at the London Conference that framed the Nuremberg Charter.8 This phrase has resonated throughout the legal and moral regimes in the post World War II era.9 M. Cherif Bassiouni commends the aptness of this phrase, as it encompasses the enormity of the underlying offenses as core violations of humanity and suggests that these offenses aggrieve all human beings regardless of their community.10 David Luban argues that “crimes against humanity” signifies that all humanity is the interested party and that humanity’s interest may differ from the interests of the victims.11 He relies on an argument made by Hannah Arendt in Eichmann in Jerusalem in which she explains:

The physical extermination of the Jewish people was a crime against humanity, perpetrated upon the body of the Jewish people […] insofar as the victims were Jews, it was right and proper that a Jewish court should sit in judgment; but insofar as the crime was a crime against humanity, it needed an international tribunal to do it justice.

Because humans are inherently social creatures, they require artificial political organizations which inevitably threaten their well-being, as was the case with the Nazi regime and the Holocaust.12 Crimes against humanity developed as a customary norm of international law in response to the very worst of those threats.13

Luban goes on to analyze the various iterations of crimes against humanity since their introduction in the Nuremberg Charter. Article 6(c) of the Nuremberg Charter sets out the definition for crimes against humanity. These crimes are typically committed against fellow nationals as well as foreigners. This category of crime was contemplated by Nuremberg because, prior to World War II, war crimes against civilian populations only covered offenses against foreign populations, whereas the Holocaust was a Nazi endeavor against their own nationals. Article 6(c) was intended to cover the gap in law to hold accountable governments who used their resources to murder their own people.14 The “unique evil” criminalized by this article is politically organized persecution and the slaughter of people under one’s own political control.15

Crimes against humanity are committed by politically organized groups acting under color of policy.16 The Nuremberg Charter presupposed that crimes against humanity were committed by agents of a state, and this nexus was deemed necessary to bring the crimes into the purview of international law.17 However, the context of the Bosnian War and the Rwandan Genocide led drafters of the ICTY Statute to weaken this “state action” requirement due to the loose affiliation of perpetrators with the state.18 The ICTR Statute replaced the “armed conflict” language of the ICTY Statute with the requirement of a “widespread or systematic attack against any civilian population on national, political, ethnic, or racial grounds,” because armed conflict implied state sanctioned action and many of the perpetrators of genocide in Rwanda were civilians with no connection to the armed conflict.19 The Rome Statute for the ICC adopted this language, but removed the requirement that the attack be on national, political, ethnic, racial, or religious grounds, and require connection of the offense to a “State or organizational policy.”20 The metamorphosis of the state action requirement for crimes against humanity into a broader element of “widespread and systematic attack” linked with a state or organizational policy shows that crimes against humanity are crimes committed through political organization. There are scholars who argue provisions of the Rome Statute are reflective of customary international law; in fact, the International Committee of the Red Cross study on customary international law is replete with references to different articles of the Statute.21 Even if crimes against humanity as articulated in the Rome Statute are not settled principles of customary international law, their evolution and subsequent ratification by state parties to the ICC are evidence of state practice. The collective agreement by states on this definition would advance the development of soft law and eventually solidify as a customary norm through processes that were impacted by the politics of World War II, the Bosnian War, and the Rwandan Genocide.

B. The Crime of Slave Trade

Another example of political processes impacting the development of customary international norms is the criminalization of slave trade and slavery. International criminal lawyer Patricia Sellers argues that the crime of slave trade has been taken out of the international community’s legal arsenal, to the disservice of victims who have been traded.22 In her argument, she details the history of the slave trade and slavery, their outlaw, and how the political focus on the prohibition of slavery has pushed it into the spotlight as a customary theory under which alleged perpetrators are prosecuted in international courts. Meanwhile, the crime of the slave trade which has elements distinct from slavery, and has a broader scope of individuals to whom it can apply, is a legal tool for prosecutors that has slid into obscurity.

Sellers explains that the U.S. and the U.K. hastened to stop the import of African slaves after the Haitian revolution, with the U.K. banning its own slave trade in 1807. The abolition movement gripped North and South America towards the end of the 19th and in the early 20th century. The 1926 Slavery Convention outlawed slavery and the slave trade, defining slave trade as all acts involved in the capture, the acquisition, or the disposal of a person with the intent to reduce him or her into slavery.23 The further exchange and transport over someone who is already a slave is still slave trade, and as long as the intent is to eventually reduce someone to slavery, the crime has occurred. This means that in a chain of slave traders trading one person, even if the person is only reduced to slavery after the fourth trade, all traders are guilty of slave trading because they possess the requisite mens rea of the crime.

However, the specter of slavery in its different forms has overshadowed charges of slave trade in modern international jurisprudence. The ICTY and ICTR Statutes enumerate enslavement as a crime against humanity, but the statutes don’t explicitly enumerate the prohibition of the slave trade as a crime against humanity.24 The Rome Statute of the ICC erases slave trade as an international crime. It is not enumerated as a War Crime under Article 8 despite the prohibition of the slave trade being an uncontroverted principle of international humanitarian law.25 Further, Article 7 of the Rome Statute describes the crime against humanity of enslavement in a peculiar form, inserting “trafficking in persons, particularly women and children” into the definition. Trafficking, however, is grounded in prohibitions against enforced prostitution and is not related to the West African or East African slave trade.

Sellers argues that the crime of slave trade from relevant international treaties has jus cogens and erga omnes obligations. Several factors may have contributed to its explicit omission in international judicial instruments as a war crime or crime against humanity, or as its own distinct international crime based on customary international law. She writes:

The Rome Statute sanctions only persons exercising powers attaching to rights of ownership, not perpetrators of the slave trade who transport or engage in any acts of the slave trade without exercising such powers. The 1926 Slavery Convention, 1956 Supplemental Slavery Convention, and Additional Protocol II condemn the slave trade as a distinct crime, not as a lesser-included offense of slavery, a form of aiding and abetting slavery, or as a ‘form’ of trafficking. Muddling the slave trade and trafficking is problematic.26

One of the reasons for this is the increased attention that the international community paid to the sexualization of slavery, leading up to the Rome Statute. This is another way in which politics has marred the development of an international norm. The tension in this created an avenue for the Office of the Prosecutor to investigate and draft policy papers examining the scope of the Court’s jurisdiction on sexual and gender-based crimes (including the crime of trafficking), which in turn impacts the investigations she chooses to bring under her Article 15 powers.27

IV. The “International Community as a Whole” is Inherently Political

The same political processes that impact the formation of customary international norms also impact the interpretation of the “international community as a whole.” The international community represents, in a classical view, the collective ethical and moral opinion of states.28 However, non-state organizations and institutions, as well as internal organizations and individuals operating without state sanction, play a part in the international community’s politics.29 To the extent that a state’s interests and identities correspond to and complement that of the political community, a state will behave and act in ways that support the values of the international community.30

The concept of an international community drives the development of jus cogens and erga omnes obligations, which are frequently cited for the development and application of international law, as explained above.31 These norms drive the integration of a community of states and the people that they represent into a community of mankind with a distinct set of higher core values.32 These designated higher purposes and values are considered non-derogable and constitute the basic elements of a world “constitution.”33

One of the leading promoters of the idea of an international community was the former secretary-general of the United Nations, Kofi Annan. In a widely quoted 1999 speech, he spoke of a shared vision of a better world for all people, as set out in the U.N. Charter.34 Humankind has a common vulnerability in the face global threats, and it responds with frameworks of international law, treaties, and human rights conventions.35

The U.N. and other international institutions are the locus of manifestation for the international community. A similar articulation of what “international community” means can be found in some of the holdings of the Permanent Court of International Justice, and its successor, the International Court of Justice, which was established at the same time as the United Nations.36

V. Conclusion

The development of customary international law and soft law norms are often impacted by the political machinations of states and their state practice regarding a rule. Examples of this are seen in the evolution of crimes against humanity in the Rome Statute, as well as the disappearance of the slave trade as a criminal charge in the international lexicon. In the same way that political process impact the development of law, they also shape the interests of the international community. Because they are rooted in the development of customary international law, the interests of the international community remain compatible with the Prosecutor’s explicit commitment to leave political considerations out of her decisions to investigate a situation because political considerations are implicitly embedded in the community and the laws with which she works.

Endnotes — (click the footnote reference number, or ↩ symbol, to return to location in text).

1. 1.

   Rome Statute of the International Criminal Court, Adopted by the United Nations Diplomatic Conference of Plenipotentiaries on the Establishment of an International Criminal Court, Jul. 17, 1998, U.N. Doc. A/CONF.183/9, as amended [hereinafter Rome Statute], Art. 15, available online. ↩

2. 2.

   Id. at Preamble. ↩

3. 3.

   See Office of the Prosecutor, Int’l Crim. Ct., available online (last visited Jun. 25, 2021). ↩

4. 4.

   Statute of the International Court of Justice, 59 Stat. 103 (Jun. 26, 1945) Art. 38, available online. ↩

5. 5.

   Patrick Dumberry, Incoherent and Ineffective: The Concept of Persistent Objector Revisited, 59 ICLQ 779 (Jul. 4, 2010), available online, doi. ↩

6. 6.

   Michael Akehurst, Custom as a Source of International Law, 47 British Y.B. of Int’l L. 1 (Nov. 1, 1976), paywall, archived, doi. ↩

7. 7.

   Alexander Orakhelashvili, Akehurst’s Modern Introduction to International Law (Dec. 3, 2018), paywall. ↩

8. 8.

   David Luban, A Theory of Crimes Against Humanity, 29 Yale J. Int’l L. 85 (2004), available online, archived. ↩

9. 9.

   Id. at 86. ↩

10. 10.

    M. Cherif Bassiouni, Crimes Against Humanity: Historical Evolution and Contemporary Application (Jul. 2011), paywall, doi. ↩

11. 11.

    Luban, supra note 8, at 88. ↩

12. 12.

    Id. at 90. ↩

13. 13.

    Id. ↩

14. 14.

    Id. at 93. ↩

15. 15.

    Id. at 94. ↩

16. 16.

    Id. at 95. ↩

17. 17.

    Id. at 96. ↩

18. 18.

    Id. ↩

19. 19.

    Statute of the International Tribunal for Rwanda, UNSC Res. 955 (Nov. 8, 1994) [hereinafter ICTR Statute], available online.

    See also Mahmood Mamdani, When Victims Become Killers: Colonialism, Nativism, and the Genocide in Rwanda 6–7 (Sep. 1, 2002), available online. ↩

20. 20.

    Rome Statute, supra note 1, Art. 7. ↩

21. 21.

    Yudan Tan, The Identification of Customary Rules in International Law, 34 Utrecht J. Int’l and Eur. L. 92 (Nov. 22, 2018), available online, doi. ↩

22. 22.

    Promise Inst. for Hum. Rts., (Still) Missing in Action: The International Crime of the Slave Trade, YouTube (Oct. 23, 2020), available online. ↩

23. 23.

    Convention to Suppress the Slave Trade and Slavery, League of Nations, 60 LNTS 253 (Sep. 25, 1926), available online. ↩

24. 24.

    Statute of the International Criminal Tribunal for the Former Yugoslavia, UNSC Res. 827 (adopted May 25, 1993, as last amended Jul. 7, 2009), available online; ICTR Statute, supra note 19. ↩

25. 25.

    General Order No. 100, Adjutant General’s Office (1863), available online. ↩

26. 26.

    Patricia Viseur Sellers & Jocelyn Getgen Kestenbaum, Missing in Action: The International Crime of the Slave Trade, 18 J. Int’l Crim. Just. 517 (May 2020), available online, archived, doi. ↩

27. 27.

    Office of the Prosecutor, ICC, Policy Paper on Sexual and Gender-Based Crimes (Jun. 2014), available online. ↩

28. 28.

    Robert Jackson, The Global Covenant: Human Conduct in a World of States (Mar. 2003), paywall, doi. ↩

29. 29.

    Tod Lindberg, Making Sense of the International Community, Council on Foreign Rel. (Jan. 2014), available online. ↩

30. 30.

    Jackson, supra note 28. ↩

31. 31.

    M. Cherif Bassiouni, International Crimes: Jus Cogens and Obligatio Erga Omnes, 59 Law & Contemp. Probs. 63, 66 (1996), available online. ↩

32. 32.

    Pemmaraju Sreenivasa Rao, The Concept of International Community in International Law: Theory and Reality, in International Law between Universalism and Fragmentation 85 (Isabelle Buffard, James Crawford, Alain Pellet & Stephan Wittich eds., Dec. 10, 2008), paywall. ↩

33. 33.

    Id. ↩

34. 34.

    Press Release, U.N., Secretary-General Examines “Meaning of International Community” in Address to DPI / NGO Conference, SG/SM/7133 (Sep. 15, 1999), available online. ↩

35. 35.

    Id. ↩

36. 36.

    Antonios Tzanakopoulos, The Permanent Court of International Justice and the “International Community”, in Legacies of the Permanent Court of International Justice 339 (Malgosia Fitzmaurice & Christian Tams eds., Apr. 21, 2012), available online. ↩