International Humanitarian Law: a primer

What does IHL do?

IHL is the body of international rules that seeks to limit the damage caused by armed conflict through regulating its conduct.

Instead of trying to prevent armed conflict, it seeks a compromise between two basic underlying principles of humanity and military necessity. It does this by:

• requiring protection of people who do not or can no longer participate in hostilities, such as civilians, the sick or wounded and prisoners of war; and
• restricting the means and methods of warfare to prohibit attacks on civilians and indiscriminate or inhumane weapons.

IHL does not determine the circumstances in which a state may resort to using force.

When and where does IHL apply?

IHL applies in any armed conflict between states, however it began, and regardless of how it is categorised by the parties. This is called International Armed Conflict (IAC).

It also applies in armed conflicts involving non-state actors. However, if the armed conflict is within a state, only a basic set of rules applies, and even then only if the armed conflict is sufficiently intense. This is called Non-International Armed Conflict (NIAC).

What are the basic rules of IHL?

The basic rules of IHL include:

• Protected persons: people who do not or can no longer take part in hostilities must always be protected and treated with humanity, whichever side they are on.
• Distinction: parties to a conflict must distinguish between the civilian population and combatants (and between civilian objects and military objectives), in order to spare the civilian population and civilian property.
• Proportionality: a combatant or military objective may be attacked only after an assessment concluding that civilian losses are not expected to outweigh the military advantage foreseen.
• Precaution: parties to an armed conflict must take constant precautions to spare civilians or civilian property when choosing targets, means and methods of attack, and when deciding where to place their own military sites.

What are the sources of IHL?

IHL is made up of treaties (including the four Geneva Conventions of 1949 and their additional protocols) and customary law.

Every state in the world has agreed to be bound by the Geneva Conventions, and many have also agreed to their additional protocols and to other IHL treaties.

Many of the rules set out in those treaties are also considered to be part of customary international law, which binds all states and other participants in armed conflict. There are further rules of customary international law which are not found in treaties.

Both treaties and customary law have evolved over the years. Many aspects have also been interpreted by judges in both domestic and international courts and tribunals, although not all of these interpretations are binding.

What are the current challenges for IHL?

Current challenges for IHL include:

• the complex nature of contemporary armed conflict and how appropriate the IAC/NIAC classification remains;
• applicability of IHL to new technologies such as cyber attacks and drones;
• how to tackle sexual violence in conflict;
• the relationship with human rights law; and
• enforcement (there is no specific court or enforcement mechanism for IHL, so it is primarily up to states to enforce).