8.1 Introduction to International Humanitarian Law

International Humanitarian Law

Core Principles and Definition

International humanitarian law (IHL) is the body of rules that limits the effects of armed conflict for humanitarian reasons. It protects people who are not (or are no longer) participating in hostilities and restricts the means and methods of warfare available to combatants. You'll sometimes hear it called the "law of war" or the "law of armed conflict."

Six core principles anchor the entire framework:

• Distinction requires all parties to differentiate between civilians and combatants, and between civilian objects and military objectives. In practice, this means combatants wear uniforms, and military facilities must be clearly marked.
• Proportionality prohibits attacks where expected civilian harm would be excessive relative to the concrete and direct military advantage anticipated. A strike on a minor target in a densely populated neighborhood, for example, would likely violate this principle.
• Military necessity permits only those actions genuinely required to accomplish a legitimate military purpose, such as destroying an enemy weapons cache. It does not justify unlimited force.
• Humanity forbids inflicting unnecessary suffering or destruction. This principle underlies bans on weapons like chemical and biological agents.
• Precaution obligates parties to take feasible steps to minimize civilian casualties before and during attacks. Advance warnings to civilian populations are one common precautionary measure.

These principles don't operate in isolation. In any given military decision, commanders must weigh distinction, proportionality, military necessity, and precaution together.

Application and Scope

IHL applies to all parties in an armed conflict, regardless of who started it. That's a crucial point: even a state acting in self-defense must follow IHL.

• It protects persons not participating in hostilities, including wounded soldiers, prisoners of war, civilians, medical personnel, and humanitarian aid workers.
• It regulates the means (weapons) and methods (tactics) of warfare, prohibiting those that cause superfluous injury or indiscriminate harm.
• It establishes mechanisms for implementation and enforcement, from the Protecting Powers system to war crimes tribunals.
• It interacts with other legal frameworks. Human rights law continues to apply during armed conflict alongside IHL, and international criminal law provides individual accountability for serious IHL violations.

History of International Humanitarian Law

Ancient and Early Modern Foundations

Rules restraining conduct in war are not a modern invention. Ancient Greek city-states observed norms about the treatment of heralds and the dead, and Islamic jurisprudence developed detailed rules of war centuries before the Geneva Conventions, including prohibitions on killing non-combatants and destroying crops.

The modern codification of IHL began in the 1860s. Henry Dunant's account of the Battle of Solferino (1859) shocked European society and led directly to two developments in 1863-1864: the founding of the International Committee of the Red Cross (ICRC) in 1863 and the adoption of the First Geneva Convention in 1864, which focused on protecting wounded soldiers on the battlefield.

The Hague Conventions of 1899 and 1907 then expanded the scope, establishing rules on the conduct of hostilities, including restrictions on aerial bombardment and naval warfare.

Modern Development and Codification

After the devastation of World War II, states negotiated the four Geneva Conventions of 1949, which dramatically expanded protections:

1. GC I — Protection of wounded and sick in armed forces in the field
2. GC II — Protection of wounded, sick, and shipwrecked at sea
3. GC III — Treatment of prisoners of war
4. GC IV — Protection of civilians

The Additional Protocols of 1977 further developed IHL. Protocol I addresses international armed conflicts, and Protocol II addresses non-international armed conflicts, filling a significant gap in the law.

Since then, treaty-making has continued to target specific weapons: the Ottawa Treaty (1997) banned anti-personnel landmines, and the Convention on Cluster Munitions (2008) prohibited cluster bombs. Emerging challenges like cyber warfare and autonomous weapon systems are now at the center of IHL debates, though binding rules in these areas remain underdeveloped.

International criminal tribunals, particularly the International Criminal Tribunal for the former Yugoslavia (ICTY) and the International Criminal Court (ICC), have also shaped IHL by interpreting its rules through case law.

Sources of International Humanitarian Law

Primary Treaty Sources

Treaties are the most authoritative source of IHL. The major ones to know:

• Geneva Conventions of 1949 and their Additional Protocols (1977) form the core. With 196 state parties, the Geneva Conventions have achieved universal ratification.
• Hague Conventions of 1899 and 1907 regulate means and methods of warfare and remain relevant today.
• Specific weapons treaties prohibit or restrict particular weapons. The Chemical Weapons Convention (1993), the Ottawa Treaty on landmines (1997), and the Convention on Cluster Munitions (2008) are key examples.
• The Rome Statute of the International Criminal Court (1998) defines war crimes and provides a permanent mechanism for prosecuting serious IHL violations.

Customary Law and Other Sources

Not all IHL is found in treaties. Customary international humanitarian law fills gaps, especially in non-international armed conflicts where treaty coverage is thinner.

• Customary IHL arises from consistent state practice combined with opinio juris (the belief that the practice is legally required). The ICRC's 2005 study identified 161 rules of customary IHL.
• Judicial decisions from the International Court of Justice (ICJ), the ICTY, and other tribunals interpret and develop IHL, though they are technically subsidiary sources.
• Military manuals and official state statements serve as evidence of what states accept as law.
• Soft law instruments, such as UN General Assembly resolutions and ICRC guidelines, influence the development of IHL even though they are not directly binding.

International vs. Non-International Armed Conflicts

One of the most important distinctions in IHL is between the two types of armed conflict, because the classification determines which rules apply.

Defining Characteristics

• International armed conflicts (IACs) occur between two or more states. The threshold is low: any use of armed force between states is sufficient to trigger IHL, even without a formal declaration of war.
• Non-international armed conflicts (NIACs) involve at least one non-state armed group fighting against a state or against another armed group. NIACs require a higher threshold: the violence must reach a certain intensity, and the non-state group must have a minimum level of organization (a command structure, the ability to sustain operations, etc.).
• Occupation is governed by IAC rules. Israel's occupation of the West Bank, for instance, is regulated by the Fourth Geneva Convention and the Hague Regulations.

Applicable Law and Status of Parties

The legal consequences of this classification are significant:

• The full body of IHL applies in IACs. In NIACs, only a more limited set of rules applies, primarily Common Article 3 of the Geneva Conventions (sometimes called a "mini-convention" because it sets baseline humanitarian standards) and Additional Protocol II.
• The principle of equality of belligerents applies in IACs, meaning both sides have equal rights and obligations under IHL regardless of the legality of the conflict itself.
• Combatant status and prisoner of war (POW) protections exist only in IACs. Captured fighters in IACs who qualify as combatants are entitled to POW status and cannot be prosecuted simply for participating in hostilities.
• In NIACs, no combatant privilege exists. Captured fighters can be prosecuted under domestic criminal law for acts of violence, even if those acts would be lawful under IHL in an IAC context.
• The legal status of non-state armed groups in NIACs remains one of the most contested areas of IHL. These groups have obligations under IHL, but the question of their rights and recognition is deeply controversial.