As the excellent Jinks/Corn/Rona series on IHL/IHR notes, there are a number of theories surrounding the interface between international humanitarian law (or the law of armed conflict) and international human rights law.  Indeed, I attended a conference last week at Duke Law School and hosted by the International Committee of the Red Cross that brought together United States and Canadian government officials, military representatives, and academics to discuss issues of interoperability in contemporary armed conflicts. This IHL/IHR conflict of laws conundrum featured prominently across a range of topics, including the use of force and detention operations.  From these conversations, the jurisprudence emerging from international tribunals, and the academic literature, it is possible to draw together a taxonomy of approaches for resolving the normative tensions that exist at the intersection of these two bodies of law.

The first theory is one of lex specialis, which comes in a strong and a weak form. The strong form envisions a total displacement of IHR upon the commencement of armed conflict. By this view, humanitarian law and human rights law are self-contained, mutually exclusive regimes. Where IHL applies but does not speak to a situation, actors are free to choose a course of action, unfettered by legal rules drawn from elsewhere. Gaps in the law are deemed purposeful in a sense such that they should not be filled from other sources.

The weak form of the lex specialis theory does not envision the total displacement of international human rights norms in armed conflict situations except where the rules of IHL and IHR are in direct contradiction. Where the applicable rules are not directly opposed to each other, or where there are gaps in IHL as the lex specialis, this approach would dictate that the two bodies of law should be harmonized through interpretive techniques and formal declarations of derogation. IHR may be particularly relevant in regulating the conduct of states engaged in NIACs, where IHL rules are less developed as compared to the corpus of rules applied to IACs.  This is the approach largely adopted by the Human Rights Committee, charged with interpreting the International Covenant on Civil and Political Rights, in its General Comment 31 and by the International Law Commission (ILC)’s Study Group on the Fragmentation of International Law.  As such, where there are gaps in IHL, there may be other rules—including human rights norms and domestic law—that are applicable. Human rights law can also be employed as an interpretive aid to add content to undefined terms in IHL, such as “judicial guarantees” and “humane treatment,” or to expound upon treaty obligations, as in situations of occupation when the occupying state exercises plenary power over territory.

While many adherents to a lex specialis approach consider human rights to be an invasive species vis-à-vis IHL, it cannot be gainsaid that positive IHL invites in these very norms. Thus, many IHL treaties create space for a consideration of, or even interlineations with, human rights norms and concerns. The Martens Clause is the precursor to this phenomenon, and Article 72 and Article 75 of Additional Protocol I are more modern and fulsome manifestations of this tendency. These textual portals go far toward debunking the lex specialis maximus approach to the humanitarian law/human rights interface. By the same measure, there are IHR treaties that specifically make allowances for situations governed by IHL. The European Convention on Human Rights, for example, specifically exempts from censure “deaths resulting from lawful acts of war.” This formulation necessarily imports elements of IHL into the human rights analysis such that in a situation of armed conflict, IHL defines what constitutes an “extrajudicial” killing.

A third approach to managing this interface rejects the idea of lex specialis and of a hierarchy of rules altogether. Instead, it presumes that the most appropriate rule or body of law should be applied in any particular scenario to promote what the ILC calls “systemic integration.” This approach may dictate application of a sliding scale between the two bodies of law depending on the circumstances. So, activities on the battlefield or in an active theater of hostilities may be governed almost exclusively by IHL, but human rights law may have more to say vis-à-vis law-of-war detention practices in light of its detailed rules on conditions of confinement and judicial protections. Thus, the applicability of IHL is not necessarily binary, in the sense that the corpus of IHL either applies in its entirety to an incident, territory, or individual, or not at all.

Finally, one can envision a reverse lex specialis prioritization, whereby international human rights norms apply to temper elements of classic IHL. This may be due to the fact that many human rights norms constitute later in time legal pronouncements. Or, this approach may be justified with reference to human rights rules’ strong normative force or jus cogens nature.  As such, the additive application of pertinent rules to ensure maximum protection to the individual.

Most courts and commentators have adopted a harmonizing approach to this question. The ICJ, for example, in the Nuclear Weapons opinion stated that IHL as the lex specialis would determine whether a particular killing was “arbitrary”:

The test of what is arbitrary deprivation of life, however, … falls to be determined by the applicable lex specialis, namely, the law applicable in armed conflict is which designed to regulate the conduct of hostilities. Thus whether a particular loss of life … is to be considered an arbitrary deprivation of life contrary to Article 6 of the Covenant [on Civil and Political Rights], can only be decided by reference to the law applicable in armed conflict and not deduced from the terms of the Covenant itself.

Even Philip Alston, the former Special Rapporteur on Extrajudicial Killing, Summary or Arbitrary Executions and fellow contributor here at Just Security, noted that targeted killings can be lawful in the context of IHL:

[A]though in most circumstances targeted killings violate the right to life, in the exceptional circumstances of armed conflict, they may be legal.

Given that there are multiple theories for how the law governing the use of force and human rights law interact, there will be situations—most notably in counterterrorism operations—when the jus in bello and international human rights norms simply cannot be perfectly harmonized because the two bodies of law permit forms of action or impose obligations and restraints that are inherently incompatible. In such situations, it comes down to a pragmatic policy choice by the state as to which body of rules to follow. This choice is, of course, subject to the recognition that the state will have to accept any consequences—reputational, reciprocal, retaliatory—for having breached an equally applicable legal obligation.