Limits of IHL

As we have just learnt, there are two types of armed conflict that trigger the application of IHL: international armed conflict (IAC) and non-international armed conflict (NIAC). Legally speaking, there are no other types of armed conflict.

It is generally accepted that, for violence between two States to amount to an IAC, the exchange of fire between those States’ armed forces – even if this is “two shots” fired – could trigger the application of IHL.

There are well-established legal criteria for determining when the threshold of violence is met for a NIAC, and this is applied on a case-by-case basis. Internal disturbances and tensions – riots, isolated and sporadic acts of violence and similar acts – within the borders of a State do not meet the requisite threshold of a NIAC.

Essentially, two requirements are necessary for a situation to be classified as a NIAC:

1. The hostilities must reach a minimum level of intensity; and
2. Groups involved in the conflict must be considered as “parties to the conflict”, meaning there is a minimum degree of organisation within the armed group (e.g. they have a certain command structure and the capacity to sustain military operations).

To help determine whether a NIAC exists, you can look to the following possible indicators (note this is not a comprehensive or definitive list):

• the number, duration and intensity of confrontations;
• the type of weapons used;
• the number of persons taking part in the fighting;
• the existence of a command structure and rules within the armed group(s);
• the existence of command headquarters; and
• the ability of the group to plan and carry out military operations.

As international law expert Nils Melzer explains, this grants States authority to use force in order to restore public order. He writes,

Given that jus ad bellum [the law concerning the right to go to war] imposes a general prohibition on the use of force between States, any such use can be legitimately presumed to express belligerent intent and to create a situation of international armed conflict, which must be governed by IHL. By contrast, within their own territory, States must be able to use force against groups or individuals for the purpose of law enforcement; and the use of force by such groups or individuals against each other or against governmental authorities generally remains a matter of national criminal law. As a consequence, the threshold of violence required to trigger a non-international armed conflict and, thereby, the applicability of IHL is significantly higher than for an international armed conflict.

Situations such as these may require authorities to deploy specialist law enforcement, such as riot police, or even the armed forces to restore peace and order, but this will not automatically invoke the application of IHL. Rather domestic law, including human rights law and national criminal law, will continue to apply. There is always a risk that such situations may escalate into armed conflict though, which in turn would invoke IHL.