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Why customary international law matters in protecting human rights


Does customary international law really matter in protecting human rights, and if so how? This was the theme of a panel at International Law Weekend in New York on October 20, 2018. International Law Weekend is an annual conference organized by the American Branch of the International Law Association. The panel was sponsored by the American Branch’s Committee on the Formation of Customary International Law, of which I serve as chair.

This blog symposium is inspired by presentations made during that conference, and include my short introduction and future posts by Alan Franklin, Managing Director of Global Business Risk Management and Faculty, Athabasca University and Diplo Foundation; Dr. Dana Schmalz, Visiting Scholar at the Zolberg Institute on Migration and Mobility at The New School; and Mark Janis, William F. Starr Professor of Law at the University of Connecticut.

The evolution of international human rights law in the seventy years since the Universal Declaration of Human Rights was adopted by the U.N. General Assembly in December 1948 has been a truly remarkable achievement in the annals of history. There now exists a panoply of treaties and additional declarations, built on the foundation of the principles enshrined in the Universal Declaration, that constitutes a veritable international human rights law order. It has transformed the global legal landscape and altered the way that government leaders think about human rights issues – compelling them to consider the human rights dimensions of their policies more seriously than ever. And the rise of international human rights law has been accompanied by a corresponding fortification and expansion of international criminal law, a body of law that seeks to hold individuals accountable for severe international crimes that themselves violate entrenched norms of international human rights law.

Much of the corpus of international human rights law takes the form of declarations and resolutions, such as the Universal Declaration itself, and treaties, such as the 1966 International Covenant on Civil and Political Rights and the 1966 International Covenant on Economic, Social and Cultural Rights.  Declarations and resolutions do not directly create legally binding obligations; for example, resolutions of the General Assembly are merely recommendations made to member states according to Article 13 of the U.N. Charter. On the other hand, treaties by themselves bind only states that have ratified them, as made clear by Article 34 of the Vienna Convention on the Law of Treaties (affirming that “a treaty does not create either obligations or rights for a third State without its consent”). However, the Vienna Convention affirms in Article 38 that a non-party to a treaty containing a particular norm can still be bound by a similar norm found in customary international law.

These foundational concepts raise important questions about how customary human rights norms are formed, and the role that U.N. resolutions and treaties play in this process. Of course, under the traditional “two-element” theory of customary law recently endorsed by the International Law Commission in its Draft Conclusions on the identification of customary international law, customary human rights norms, like all customary norms, arise from the convergence of uniform state practice and opinio juris. Thus, ILC Draft Conclusion 2 affirms: “To determine the existence and content of a rule of customary international law, it is necessary to ascertain whether there is a general practice that is accepted as law.” See also Michael Wood, Forewordin Reexamining Customary International Law xiv (Brian D. Lepard ed., 2017).

However, in the case of human rights norms, the actual “practice” of states respecting human rights is mixed at best; very often states engage in egregious affronts to human dignity and rights. Does this necessarily prevent a customary norm from emerging? Both courts and scholars have tended to err on the side of viewing negative human rights behavior on the part of governments as reflecting violations, not as practice helping to establish a rule permitting such transgressions.

It is also often challenging to apply the traditional doctrine of opinio juris – defined as a belief by states that a particular norm already is law – to human rights norms. One reason is that it is difficult to determine whether states believe that a putative norm is law. Even if the norm is declared in a resolution, states voting in favor of the resolution may view the norm as aspirational, not as existing law, in keeping with the formal status of the resolution as a recommendation. Nevertheless, states that vote in favor of the resolution may well believe that it is desirable to recognize the norm as law. By the same token, the fact that a state has ratified a treaty and agreed to be bound by human rights norms in it does not necessarily indicate that the state believes there already is a norm binding all states apart from the treaty – the necessary belief under the traditional definition of opinio juris. Yet that state may very well wish that other states would follow its example in ratifying the treaty and that the norms proclaimed in it ought to bind all states.

Because of these deficiencies in the traditional two-element definition of customary international law, I have proposed a new definition according to which a new customary norm emerges when “states generally believe that it is desirable now or in the near future to have an authoritative legal principle or rule prescribing, permitting, or prohibiting certain conduct.” See Brian D. Lepard, Customary International Law: A New Theory with Practical Applications 8 (2010). In essence, this definition looks to opinio juris as the core of customary law and also re-envisions opinio juris as a forward-looking belief regarding what the law ought to be, now or in the near future, not merely what it is. And I have suggested that fundamental ethical principles related to a foundational principle of “unity in diversity” ought to play a critical background role in identifying customary law norms where state beliefs are ambiguous. See id. at 78-81.  

Despite some of the methodological problems apparent with applying the traditional two-element definition of customary international law to human rights violations, both national and international courts and tribunals are increasingly identifying and applying customary human rights norms. They have applied them not only to the actions of governments, but also the conduct of businesses and non-state actors. (For a discussion on this blog of business and international human rights law see here.)

In the U.S., the Alien Tort Statute (“ATS”) has been invoked by federal courts to find both individuals and corporations liable for violations of the customary human rights standards, including, among others, torture – often on the ground that they have colluded with foreign governments in committing these atrocities. It is true that the U.S. Supreme Court has recently narrowed the permissible scope of these actions, including holding that a claim under the ATS must in some way “touch and concern” the U.S. (in Kiobel v. Royal Dutch Petroleum, decided in 2013), and that foreign corporations as such cannot be sued under the statute (in Jesner v. Arab Bank, decided in 2018). However, this litigation is likely to persist and simply exemplifies a broader global trend of courts applying customary human rights law to provide some redress for victims.

Accordingly, despite recent claims that customary international law is no longer of great importance in view of the proliferation of treaties, the evidence suggests that customary international law is playing a more vital, rather than waning, role in the protection of human rights.

Despite this enhanced role, many important questions abound – some of them alluded to earlier – that are addressed by the authors who will be contributing to this symposium. For example, can customary international law directly bind corporations? Can corporations be subjects of customary international law? Even if they can, is it appropriate to hold the corporations, as opposed to foreign governments, liable, especially when foreign governments or forces are the actors directly responsible for human rights violations? Are there risks of expanding direct liability under customary law for corporations? Certainly the U.S. Supreme Court expressed concerns such as these in the Jesner case, decided in April 2018, in which it questioned whether corporations, rather than individuals, can commit human rights violations. In part on the basis of such doubts, it held that the ATS can no longer provide a forum for lawsuits against non-U.S. corporations. Importantly, however, the Supreme Court explicitly left the door open to suits against individual corporate officers.

The issue of liability of corporations under customary international law raises another set of intriguing questions relating to the role of customary human rights law in domestic legal orders. Most countries incorporate customary international law in the domestic legal order in some way. For example, the U.S. Supreme Court has declared that customary international law “is part of our law” (see The Paquete Habana, decided in 1900) and it is generally understood to form part of the federal common law. Other common law jurisdictions, taking inspiration from Blackstone, generally treat customary law as part of their common law. Civil law countries have their own mechanisms for incorporating customary law, often through constitutional provisions. All of these approaches raise important issues about just how customary human rights norms are or ought to be applied as part of domestic law – and whether applying domestic law may provide an alternative to holding actors (including corporations) directly liable under customary international law. Alan Franklin will take up these and other questions in his symposium contribution.

Another set of questions revolves around the role of international resolutions, declarations, and informal agreements as evidence of either state practice, opinio juris, or both. For example, a long-running debate has raged on to what extent the Universal Declaration itself evidences these elements of customary international law. Many commentators argue that expressions of support by governments for the principles in the Declaration can constitute both the requisite state practice and opinio juris, such that many, if not all, of the norms in that milestone document can now be considered customary law binding on all states.

Can a similar line of reasoning apply to other non-treaty documents, such as the Global Compact on Refugees, adopted in December 2018? Moreover, can there be such a swell of state support for particular principles in a resolution – such as a principle of burden-sharing regarding acceptance of asylum-seekers – that those principles can become customary law very quickly, if not instantly? What role should ethics play in such a determination, especially where compelling ethical principles (such as a principle of respectful and humane treatment of refugees and asylum-seekers) would support greater burden-sharing? These are some of the problematic issues taken up by Dr. Dana Schmalz in her contribution to this symposium.

Returning to the role of customary human rights law in relation to human rights treaty law, courts have often looked to human rights treaties as evidence of customary law norms – especially when those treaties (such as, for example, the ICCPR) are widely ratified and have been endorsed by states over a very long period of time (in the case of the ICCPR, over 40 years since its entry into force in 1976). In such cases, customary law often “piggybacks” on treaty norms. But are there areas in which customary law may (and should) actually provide greater protections for human rights than treaties?  Can customary law therefore serve a critical function in the international legal order by supplementing more restrictive treaty norms?

Furthermore, does customary law have certain advantages over treaty law by virtue of its freedom from the types of self-interested motivations that can affect the drafting of treaty texts and their interpretations by courts? More expansively, can customary law enjoy such freedom in part because of the greater role that jurists and scholars can and should play in the identification of customary law norms? Finally, as I have suggested above, can customary law also have an advantage over treaties to the extent that ethical principles – including “unity in diversity” – ought to play a critical background role in the identification of customary law norms? Mark Janis, in his contribution to the symposium, will touch on these types of questions in relation to the protection of the freedom of belief of members of minority religions.

Our hope is that this symposium will expand an important discussion of how and why customary international law today matters in protecting the human rights of all human beings.


Brian D. Lepard is the Harold W. Conroy Distinguished Professor of Law at the University of Nebraska College of Law.


Cite as: Brian D. Lepard, “Why Customary International Law Matters in Protecting Human Rights”, Völkerrechtsblog, 25 February 2019, doi: 10.17176/20190225-133150-0.

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