ESIL-International Human Rights Law Symposium: Interactions Between IHRL and Other Sub-branches of International Law – A Research Agenda

In our first post as co-chairs of the ESIL Interest Group on Human Rights, we suggested that human rights are central organising principles of public international law. We noted that:

International human rights law routinely interacts with other sub-branches of public international law by demanding new interpretations of existing law (cf. the principle of territorial application of treaties as regulated in the Vienna Convention on the Law of the Treaties); by qualifying existing obligations under other bodies of law (cf. international human rights law and the law of occupation); or imposing procedural and substantive obligations onto other bodies of law (cf. the ICC Statute).

In this symposium, we deepen our inquiry into the relationship of international human rights law (IHRL) with other sub-branches of public international law. We do so by examining in what ways and the extent to which IHRL has shaped and influenced the development of international criminal law, the law of armed conflict, international investment law, cultural heritage law and development. Looking at interactions between IHRL and a number of other sub-branches of public international law (PIL) demonstrates that there are both divergences and convergences in why and how far IHRL influences other bodies of PIL.

The contributions in this symposium indicate that all sub-branches under discussion interact with IHRL. There are, however, significant variations in how far they interact, the terms of interaction and the assessments of the consequences of such interaction. What explains such variation? Our contributors identify push and pull factors.

The purposive affinity between IHRL and other branches of PIL emerges as an important factor supporting IHRL’s influence on other branches. Lixinski on international cultural heritage law, Murray and Hampson on international humanitarian law, and Cryer on international criminal law, all point out that interactions with IHRL are strong because there are overlaps between what these bodies of law are seeking to achieve and IHRL. Van Ho’s post, on the other hand, points to the perceived lack of purposive affinity between IHRL and international investment law accounting for the limited interaction between the two sub-branches.

Contributors identify push factors, however. The first, and obvious push factor is the location of interaction. In some cases, low levels of interaction can be attributed to the fact that the decision-making body does not have direct jurisdiction to make a finding of a violation of IHRL or may be unclear on how far it can use IHRL to shape its decision (just as human rights tribunals are often unclear on how to take into account other sub-branches such as the law of armed conflict when determining whether a state has violated human rights). For example, Van Ho’s post illustrates the difficulties faced by international investment tribunals in dealing with IHRL.

The second push factor is difference in historical trajectories. McInerney-Lankford, for example, argues that despite purposive affinity, interaction between IHRL and development law is less than might be expected, due to different historical trajectories and institutional cultures through which development law is made and applied.

A central insight that emerges from the contributions is that even if sub-branches have a purposive affinity with IHRL, this is only a part of the story. All branches of international law share a common concern over ‘branch-autonomy’ in relation to interpretive insights outside of their own domain.

Cryer and Lixinski both suggest that certain sub-branches of international law can resist interaction with IHRL in order to preserve their own autonomy. For example, Cryer cautions against simplistic characterisations of the relationship between international criminal law and IHRL because of their shared jurisdiction over crimes under international criminal law that would also be viewed as serious violations of international human rights law. He observes that while the international criminal tribunals originally ‘drew upon the work of human rights bodies’, they quickly began to distinguish the sub-branches. This distinction was based on the different subject-matters of IHRL and international criminal law, with the former regulating state responsibility which Cryer suggests allows for an ‘appropriately progressive interpretation’ and the latter requiring a more conservative approach due to its focus on individual criminal responsibility.

Murray and Hampson highlight that in the field of international humanitarian law, arguing for branch autonomy serves the purpose of protecting the effectiveness of international humanitarian law on the battlefield. They caution against displacing practical regulation with unrealistic standards in the name of greater interaction between IHRL and international humanitarian law.

The most explicit manifestation of attempts to preserve branch-autonomy is highlighted by Lixinski. He acknowledges the contributions of IHRL to cultural heritage law through rights of access, participation and identity. However, he also cautions that IHRL can risk the co-option of ‘all of heritage under the umbrella of a “human rights approach” with the potential to narrow and stifle the development of the field.

The contributions reveal that the relationship between IHRL and other sub-branches is therefore either overlooked or addressed in terms of which sub-branch ‘trumps’ the other. This happens through variations of a lex specialis or through resistance and distinction of IHRL due to its perceived dominance and potential to ‘overtake’ and stagnate the development of other sub-branches or threaten branch-autonomy.

The focus on these debates, while important, reveals an under-determination of how and when IHRL and another sub-branch of PIL should co-regulate and co-apply to an issue as well as how IHRL should and can adapt to contexts in which it was not originally designed to apply. In this symposium, Murray and Hampson reflect on the need to move away from lex specialis towards a more nuanced conversation on the interpretation and application of IHRL (including by human rights bodies such as the European and Inter-American Courts of Human Rights) with the operational choices of conflict in mind. Similarly, Van Ho suggests that some bright lines can be drawn where IHRL should always ‘trump’ international investment norms in investment-state arbitrations. Outside of these areas, she also submits that a more careful management of the relationship between IHRL and international investment law is needed by engaging and developing the ‘reasonableness’ test.

These contributions indicate the need for greater efforts to develop and deepen the co-regulation of issues in international law by more than one branch and for IHRL to mature and adapt to new contexts and new relationships such as investor-state relationships that were not originally foreseen at the time of the development of IHRL.