All parties to an armed conflict – whether States or organized non-State armed groups – are bound by treaty and customary rules of IHL. Rules of customary IHL apply at all times to all parties, irrespective of their ratification of IHL treaties.

States and their obligations
Only States may become parties to international treaties such as the Geneva Conventions and their Additional Protocols. As of November 2013, 195 States were party to the Geneva Conventions. The fact that the Conventions are all but universally ratified testifies to their importance.
As of March 2014, 173 States were party to Additional Protocol I, 167 to Additional Protocol II and 66 to Additional Protocol III.

Organized non-State armed groups and their obligations
Organized non-State armed groups are bound – as parties to non’international armed conflict – by common Article 3 and Additional Protocol II (if the threshold for its application is met – see Question 5) provided that the State to which they belong is party to the treaties in question. In any case, they are also bound by customary IHL rules pertaining to non’international armed conflicts.

National liberation movements
National liberation movements fighting against colonial domination and alien occupation and against racist régimes in the exercise of the right of self-determination of the peoples they represent may undertake to apply the Geneva Conventions and Additional Protocol I (i.e. IHL pertaining to international armed conflicts) by means of a unilateral declaration addressed to the depositary, i.e. the Swiss Federal Council. (See Article 1, paragraph 4, and Article 96, paragraph 3, of Additional Protocol I).

Does IHL apply to peace operations carried out by or under the auspices of the United Nations?
The multifaceted nature of peace operations and the ever more difficult and violent environments in which their personnel operate make it more likely that multinational forces conducting such operations will become involved in the use of force. In such situations, the question of IHL applicability becomes very pertinent.

The issue of IHL applicability to multinational forces has been disregarded for a long time. It has often been contended that United Nations forces cannot be party to an armed conflict, and therefore cannot be bound by IHL. It has also been affirmed that multinational forces, which bear the stamp of international legitimacy, should be considered to be impartial, objective and neutral, because their only interest in any armed conflict is the restoration and preservation of international peace and security.

This view of the matter, however, dispenses with the longstanding distinction between jus ad bellum and jus in bello. As with anyone else, the applicability of IHL to multinational forces must be determined solely on the basis of the facts, irrespective of the international mandate assigned to multinational forces by the Security Council and of the designation given to the parties potentially opposed to them.

IHL will be applicable to multinational forces once they become party to an armed conflict, be it international or non-international. When multinational forces are fighting against State armed forces, the legal framework of reference will be IHL applicable to international armed conflict. When they are opposed by one or more organized non-State armed groups, the legal framework of reference will be IHL applicable to non-international armed conflict.

Peacekeeping and peace-enforcement operations
Peace operations are often divided into two categories: peacekeeping and peace-enforcement. The purpose of peacekeeping operations is to ensure respect for ceasefires and demarcation lines and to conclude troop withdrawal agreements. In the past few years, the scope of peacekeeping operations has been widened to cover other tasks, such as supervision of elections, forwarding of humanitarian relief, and provision of assistance in the process of national reconciliation. Members of peacekeeping forces are authorized to use force only for purposes of self-defence. Such operations take place with the consent of the parties concerned.

Peace-enforcement operations, which come under Chapter VII of the United Nations Charter, are carried out by United Nations forces or by States, groups of States or regional organizations, either at the invitation of the State concerned or with the authorization of the United Nations Security Council. These forces are given a combat mission and are authorized to use coercive measures for carrying out their mandate. The consent of the parties is not necessary.

The distinction between these two types of operation has become less clear in recent years, since peace operations often carry out tasks that are typical of both peacekeeping and peace-enforcement operations. As a result, the more general terms ‘peace support operations’ and ‘peace operations’ are being used more frequently now.

The nature of the peace operation’s mandate and its designation – peacekeeping or peace-enforcement – has no bearing on IHL applicability, which is determined on the basis of the facts and of the fulfilment of the criteria for armed conflicts stemming from the relevant IHL provisions, in particular, common Articles 2 and 3.

The obligation to respect and ensure respect for IHL
It is not only the parties to an armed conflict that have obligations under IHL. All States – and the international community as a whole – must “respect and ensure respect” for IHL.

This phrase can be found in common Article 1, which states: “The High Contracting Parties undertake to respect and to ensure respect for the present Convention in all circumstances.” (See also Article 1, paragraph 1, of Additional Protocol I.)
The obligation of parties to a conflict to respect and ensure respect also exists in customary IHL. (See Rule 139 of the ICRC’s study on customary IHL.)
• “To respect” means that parties to IHL treaties must apply these treaties in good faith.
• “To ensure respect” has a broader meaning: States party to IHL treaties, whether engaged in a conflict or not, and the international community as a whole, must take all possible steps to ensure that the rules are respected by all, and in particular by parties to conflict.

Whose duty is it to spread knowledge of the Geneva Conventions and their Additional Protocols?

States have a legal obligation to spread knowledge of the Conventions and their Additional Protocols:

“The High Contracting Parties undertake, in time of peace as in time of war, to disseminate the text of the present Convention as widely as possible in their respective countries, and, in particular, to include the study thereof in their programmes of military and, if possible, civil instruction, so that the principles thereof may become known to the entire population, in particular to the armed fighting forces, the medical personnel and the chaplains.” (Articles 47 and 48 of the First and Second Geneva Conventions respectively. See also Articles 127 and 144 of the Third and Fourth Geneva Conventions respectively.)

“The High Contracting Parties undertake, in time of peace as in time of armed conflict, to disseminate the Conventions and this Protocol as widely as possible in their respective countries and, in particular, to include the study thereof in their programmes of military instruction and to encourage the study thereof by the civilian population, so that those instruments may become known to the armed forces and to the civilian population.” (Article 83 of Additional Protocol I.)

“This Protocol shall be disseminated as widely as possible.” (Article 19 of Additional Protocol II.)