Domestic law and human rights law both apply to all types of violence, whereas IHL applies only to situations that reach the level of armed conflict.

Here, it should be noted that the terms ‘armed conflict’ and ‘war’ are often used interchangeably, but in IHL ‘armed conflict’ is preferred because of its broader scope. A state of armed conflict can be said to exist when two opposing States resort to armed force even when no formal declaration of war has been made, or even when the parties involved in hostilities do not acknowledge the fact that they are in a state of armed conflict.

IHL also distinguishes between two types of armed conflicts:
International Armed Conflict and Non-International Armed conflict.

Different sets of IHL rules apply to different situations of armed conflict.

During international armed conflicts, the four Geneva Conventions of 1949 apply, as does Protocol I additional to the Geneva Conventions (Additional Protocol I of 8 June 1977).

The four Geneva conventions are:
– Convention I, protecting the wounded and sick in armed forces in the field;
– Convention II, protecting wounded, sick and shipwrecked members of armed forces at sea;
– Conventions III, protecting prisoners of war;
– Convention IV, protecting civilian persons in time of war.

An international armed conflict may be said to occur when one or more States have recourse to armed force against another State, regardless of the reasons for or the intensity of this confrontation.

No formal declaration of war or recognition of the situation is required. For example, there may be an international armed conflict even though one of the belligerents does not recognize the government of the adverse party. Further, Additional Protocol I extends the definition of international armed conflict to include armed conflicts in which people are fighting against colonial domination, alien occupation or racist regimes in exercise of their right for self-determination.

An international armed conflict is said to occur when there is any use of force between two or more States, whereas the territory of a State is considered to be “occupied“ when another State has effective control over all or part of it.

On the other hand, during a non-international armed conflict, Article 3 common to the four Geneva Conventions applies to all situations.

Protocol II additional to the Geneva Conventions (Additional Protocol II), which further develops, clarifies, and complements common Article 3, applies when one or several non-state armed groups opposed to the armed forces of a State exercise a level of control over a part of the territory of the State that allows them to conduct military operations.

In both situations the relevant provisions of customary international humanitarian law apply.

As a conclusion, IHL only applies to situations of armed violence between States or situations reaching the level of a non-international armed conflict (minimum level of intensity, between organized armed forces).