Introduction
The traditional understanding of the law governing armed conflict places International Humanitarian Law (IHL) as the primary and specialised legal regime. As Stuart Casey-Maslen (2015) notes, the suggestion that International Human Rights Law (IHRL) provides an "overarching international legal framework" for issues like weapons legality can seem counter-intuitive. Historically, IHRL was seen as the law for peacetime, suspended or displaced during armed conflict in favour of IHL, a principle known as lex specialis. However, contemporary international law increasingly views these two disciplines as complementary and co-applicable. This essay will argue that the application of both IHRL and IHL together generally provides greater and more comprehensive safeguards for individuals. While IHL remains the specific law for the conduct of hostilities, IHRL offers a persistent framework of protection that fills gaps, reinforces norms, and provides enhanced accountability mechanisms. This will be demonstrated through an analysis of weapons law, the prohibition of torture, and the prohibition of sexual violence, concluding that the advantages of their concurrent application largely outweigh the disadvantages, which are primarily confined to areas of direct conflict.
The Evolving Relationship: From Lex Specialis to Complementarity
The principle of lex specialis derogat legi generali suggests that a special law derogates from a general law. In the context of armed conflict, IHL has long been considered the lex specialis, with its detailed rules on targeting, detention, and treatment of persons, which were thought to override the more general provisions of IHRL (Sassòli, 2019). This view assumes a clear distinction between states of peace and war, with different legal codes for each.
However, this rigid separation has been dismantled by international jurisprudence. The International Court of Justice (ICJ) has been central to this shift. In its Legality of the Threat or Use of Nuclear Weapons advisory opinion, the court affirmed that "the protection of the International Covenant on Civil and Political Rights does not cease in times of war" (ICJ, 1996, para. 25). It clarified that the right to life is not to be interpreted in isolation; rather, what constitutes an arbitrary deprivation of life under IHRL must be determined by the applicable lex specialis, namely IHL, in a situation of armed conflict. This was reiterated in the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory advisory opinion, where the ICJ stated that some rights may be exclusively a matter for IHL, some exclusively for IHRL, but others "may be matters of both these branches of international law" (ICJ, 2004, para. 106).
This establishes a relationship not of displacement, but of co-application and complementarity. IHL provides the specific rules for the unique circumstances of hostilities, while IHRL provides a baseline of protection that applies at all times to all individuals within a state's jurisdiction. IHRL can therefore fill gaps where IHL is silent or less protective, and its institutional mechanisms can reinforce IHL norms.
Weapons Law: A Point of Tension and Advantage
Casey-Maslen's (2015) assertion is perhaps most bold in the field of weapons law, an area traditionally dominated by IHL. The primary IHL rules for assessing the legality of a weapon are the prohibition on causing superfluous injury or unnecessary suffering and the principle of distinction, which requires that weapons are capable of being directed at military objectives (Additional Protocol I to the Geneva Conventions 1977, Arts. 35, 51). This framework is primarily concerned with regulating how weapons are used in hostilities.
The application of IHRL, specifically the right to life, introduces a different paradigm. The right to life, as articulated in Article 6 of the International Covenant on Civil and Political Rights (ICCPR), protects against the 'arbitrary' deprivation of life. In a law enforcement context, this is interpreted very strictly, requiring that lethal force only be used as a last resort where strictly necessary to protect against an imminent threat of death or serious injury (UN Human Rights Committee, 2019). Applying this standard to the battlefield would be a distinct disadvantage, as it is incompatible with the reality of combat where the enemy may be targeted based on status as a combatant, not on their imminent threat. Here, the lex specialis principle correctly identifies IHL's targeting rules as the appropriate standard.
However, IHRL provides distinct advantages outside the narrow context of active hostilities. It provides a legal framework for a state's obligations regarding the design, testing, acquisition, and transfer of weapons systems. A state has a human rights obligation to ensure its agents (police or military) are equipped with weapons that allow for the graduated use of force. Furthermore, IHRL can govern the use of force in situations that do not meet the threshold of an armed conflict, such as internal disturbances or riots, where IHL would not apply. The European Court of Human Rights, for instance, has a developed case law under Article 2 of the European Convention on Human Rights on the use of lethal force by state agents, which provides a level of scrutiny IHL does not (see McCann and Others v UK (1995)). Therefore, while IHL governs the use of weapons in combat, IHRL provides a crucial and greater safeguard that regulates a state's conduct concerning weaponry in a much broader range of circumstances.
The Prohibition of Torture: An Example of Mutual Reinforcement
The prohibition of torture and cruel, inhuman, or degrading treatment (CIDT) is a powerful example of where the two legal regimes provide mutually reinforcing protections. IHL unequivocally prohibits torture and CIDT. This is a fundamental guarantee of Common Article 3 to the four Geneva Conventions of 1949, applicable in non-international armed conflicts, and is afforded to prisoners of war and civilians in international armed conflicts.
IHRL provides an absolute and non-derogable prohibition on torture, as seen in Article 7 of the ICCPR and Article 3 of the European Convention on Human Rights. The key advantage offered by IHRL is not a differing standard, but the strength of its absolute prohibition and the enforcement mechanisms that accompany it. Human rights treaties have established monitoring bodies, such as the UN Committee against Torture and the European Committee for the Prevention of Torture, which have mandates to investigate allegations and inspect places of detention, even during armed conflict.
Furthermore, the jurisprudence of human rights courts, such as the European Court of Human Rights in cases like Al-Skeini and Others v UK (2011), has extended the application of human rights law to the conduct of states acting extraterritorially. This means that a state's agents are bound by human rights obligations, including the absolute prohibition of torture, when detaining individuals during military operations abroad. This provides an additional layer of legal accountability that complements the IHL framework of grave breaches and war crimes. In this domain, the application of both disciplines creates no real disadvantage; instead, it provides a more robust legal and institutional framework for protecting individuals from one of the most severe violations of human dignity.
Prohibiting Sexual Violence: A Broader and Deeper Protection
The prohibition of sexual violence is another area where the combined application of IHL and IHRL provides greater safeguards. While IHL has always prohibited rape and sexual assault, it was historically framed as an attack on a woman's "honour" rather than as a violent crime in its own right (Geneva Convention IV 1949, Art. 27). Modern IHL, particularly through the statutes and jurisprudence of the ad hoc international criminal tribunals and the International Criminal Court, has significantly advanced, now clearly recognising rape and other forms of sexual violence as grave breaches, war crimes, and crimes against humanity (Rome Statute of the International Criminal Court 1998, Arts. 7-8).
IHRL complements this by framing sexual violence as a violation of fundamental rights, including the right to be free from torture and CIDT, the right to physical integrity, and the right to privacy. This human rights-based approach offers a distinct advantage by providing a more victim-centred perspective, focusing on the inherent dignity and autonomy of the individual rather than just the rules of warfare (Clapham, 2006). It helps to ensure that sexual violence is understood not merely as an unfortunate by-product or tactic of war, but as a fundamental human rights violation that a state has a positive obligation to prevent, investigate, and punish at all times, whether in peace or war. The comprehensive nature of the IHRL framework, which addresses systemic discrimination and inequality, also provides tools for addressing the root causes of sexual and gender-based violence, an advantage that the more functionally-focused IHL does not offer to the same extent.
Conclusion
In conclusion, the contemporary interaction between IHL and IHRL offers significantly greater and more nuanced protections for individuals than either body of law could in isolation. While the "heresy" Casey-Maslen (2015) alludes to might be an overstatement, the overarching relevance of IHRL is undeniable. The two legal regimes are not rivals but partners in the regulation of state violence. IHL provides the indispensable lex specialis for the unique exigencies of combat, particularly in relation to targeting and the use of weapons in hostilities. Attempting to supplant these specific rules with the general standards of IHRL would be unworkable and a clear disadvantage. However, in almost every other area, the concurrent application of IHRL offers distinct advantages. It provides a universal baseline of non-derogable protections, such as the prohibition of torture; it fills temporal and jurisdictional gaps where IHL does not apply; it offers a broader, more victim-centred understanding of harms like sexual violence; and it brings powerful monitoring and accountability mechanisms to bear. The modern approach, confirmed by the ICJ, is one of harmonious interpretation, where IHRL establishes the general rule and IHL acts as a specific interpretative tool. This complementarity ensures that the fundamental goal of both disciplines – the protection of human life and dignity – is more effectively realised.
References
Al-Skeini and Others v The United Kingdom (2011) App no 55721/07, ECHR 2011.
Casey-Maslen, S. (2015) Weapons Under International Human rights Law. Cambridge University Press.
Clapham, A. (2006) Human Rights Obligations of Non-State Actors. Oxford University Press.
Convention for the Protection of Human Rights and Fundamental Freedoms (European Convention on Human Rights, as amended) (ECHR).
Geneva Convention relative to the Protection of Civilian Persons in Time of War (Geneva Convention IV), 12 August 1949, 75 UNTS 287.
International Court of Justice (ICJ) (1996) Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Reports 1996, p. 226.
International Court of Justice (ICJ) (2004) Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion, ICJ Reports 2004, p. 136.
International Covenant on Civil and Political Rights (ICCPR) 16 December 1966, 999 UNTS 171.
McCann and Others v The United Kingdom (1995) App no 18984/91, ECHR 1995.
Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), 8 June 1977, 1125 UNTS 3.
Rome Statute of the International Criminal Court, 17 July 1998, 2187 UNTS 90.
Sassòli, M. (2019) International Humanitarian Law: Rules, Controversies, and Solutions to Problems Arising in Warfare. Edward Elgar Publishing.
UN Human Rights Committee (2019) General comment No. 36, Article 6: right to life, UN Doc CCPR/C/GC/36.
