The Practical Guide to Humanitarian Law

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A large variety of weapons exist, and they can be used in many different ways.

International humanitarian law regulates the use of weapons:

  • Some weapons are simply prohibited, as such: not only is their use strictly prohibited, but so is their production, transfer, and stockpiling.
  • Other weapons are authorized, but their use is regulated by prohibiting certain forms of use; for instance, any use that is indiscriminate or disproportionate is prohibited.
  • States must examine whether any new weapon is compatible with the principles of international humanitarian law, in consultation with the ICRC.

Humanitarian Law Limits the Choice of Weapons

In general, humanitarian law prohibits any weapon “of a nature to cause superfluous injury or unnecessary suffering” and any that may have indiscriminate or excessively injurious effects. This is an ancient principle, linked to the axiom that “the right of the parties to the conflict to choose methods or means of warfare is not unlimited” (API Art. 35).

Humanitarian law may therefore prohibit the use, production, stockpiling, or selling of certain kinds of weapons. This is now the case for biological and chemical weapons, for instance, and to some extent for landmines. Since 1977 (when Additional Protocol I to the 1949 Geneva Conventions was adopted), humanitarian law has also codified that it is forbidden to employ methods or means of warfare that are intended, or may be expected, to cause widespread, long-term, and severe damage to the natural environment (API Art. 35).

For the most part, the rules governing the use of such weapons are set forth in specific international conventions that address these issues specifically and therefore only apply to the States Parties to these conventions. The main exceptions are the Geneva Conventions and Additional Protocols, which are widely ratified by States as well as carrying a status of customary international law, and which go a long way toward regulating means and methods of warfare. ▸ International humanitarian awMethods (and means) of warfare

Furthermore, in the study, development, acquisition, or adoption of a new weapon, States are under the obligation to determine whether the use of this weapon would be prohibited by humanitarian law, in some or all circumstances (API Art. 36). The International Committee of the Red Cross (ICRC) has a consultative role to play with regard to this question.

Humanitarian Law Limits the Ways Weapons Are Used

The four 1949 Geneva Conventions and their two 1977 Additional Protocols set forth the restrictions on the use of weapons. Today, these rules are mandatory for all States. Some of the main rules are as follows:

  • Parties to the conflict must distinguish between civilian and military objects. The weapons they use must always allow them to respect this distinction.
  • Weapons must not be used in a way that would not be justified by a genuine military requirement or that would be disproportionate to the military advantage sought or to the supposed military threat. The aim of these provisions is to limit superfluous, gratuitous, or unnecessary damage or suffering.
  • During attacks, parties to the conflict (in particular, their commanders) are under the obligation to take certain precautions to limit their possible effects on civilians and civilian objects.

AttacksDuty of commanders

Customary international humanitarian law also regulates the use of weapons. Rule 70 of the study on the rules of customary international humanitarian law published by the ICRC in 2005 (customary IHL study) provides that “the use of means and methods of warfare which are of a nature to cause superfluous injury or unnecessary suffering is prohibited”; while Rule 71 states that “the use of weapons which are by nature indiscriminate is prohibited.” Those two rules are applicable in both international and non-international armed conflicts.

Another important landmark in restricting the use of weapons, in a more general way, was the adoption of the Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or Have Indiscriminate Effects (known as the Convention on Conventional Weapons), in Geneva on 10 October 1980 (ratified in April 2013 by 116 State Parties), and its Additional Protocol on Blinding Laser Weapons, adopted in Vienna on 13 October 1995 (ratified by 104 State Parties in April 2013).

Categories of Weapons

Different kinds of weapons are available. Some weapons are authorized, except certain uses thereof (edged weapons and firearms), while others are strictly prohibited (incendiary, biological, and chemical weapons). The general rule that prohibits attacks against civilians is applicable to the use of all weapons.

Edged Weapons

These are any offensive or cutting blades or other weapons made of metal or steel, such as knives, swords, machetes, daggers, or bayonets. Their use is restricted by the general rules of humanitarian law, which prohibit attacking non-combatants, killing or wounding treacherously, and causing superfluous injury or unnecessary suffering (Art. 23 of Hague Convention IV; API Arts. 35–37).


This is a very broad category of weapons, including all those that shoot cartridges or explosive projectiles, such as shotguns, cannons, bombs, missiles, cluster munitions, and so on. Only some of these weapons are prohibited:

  • explosive projectiles that weigh less than four hundred grams (fourteen ounces), as established by the 1868 St. Petersburg Declaration Renouncing the Use, in Time of War, of Certain Explosive Projectiles;
  • bullets that expand or flatten easily in the human body, as set forth in the 1899 Hague Peace Declarations;
  • any weapon the main effect of which is to injure by fragments that are not detectable by X-rays once inside the human body, as established by Protocol I to the 1980 Convention on Conventional Weapons (Protocol on Non-detectable Fragments);
  • cluster munitions, as established by the Convention on Cluster Munitions adopted in Dublin in 30 May 2008 and entered into force in August 2010, which prohibits all use, stockpiling, production, and transfer of cluster munitions. As of June 2015, 92 States have ratified it. In order to monitor the application of the Convention, it has been decided that States Parties shall meet regularly in order to take decisions in respect of any matter with regard to the application or implementation of the Convention, including the operation and status of the Convention. The First Assembly of State Parties was held in Vientiane, in Laos, from 9 to 12 September 2010. The second Assembly was in Beirut, Lebanon, from 12 to 16 September 2011. Moreover, a Review Conference shall be convened by the Secretary-General of the United Nations five years after the entry into force of this Convention (Art. 12). The purpose of this Review Conference is, inter alia, to review the operation and status of this Convention.

On 30 April 2010, the Central African Convention for the Control of Small Arms and Light Weapons, Their Ammunition, Parts, and Components That Can Be Used for Their Manufacture, Repair, and Assembly, known as the Kinshasa Convention, was signed in Brazzaville, Republic of the Congo, at the Thirty-fifth Ministerial Meeting of the United Nations Standing Advisory Committee on Security Questions in Central Africa. The eleven signatories are Angola, Burundi, Cameroon, the Central African Republic, Chad, the Democratic Republic of Congo, Gabon, the Republic of Congo, Rwanda, Sao Tomé, and Principe and Equatorial Guinea. The Convention has not yet entered into force and will do so once it is ratified by six signatories. The purpose of this Convention is to prevent, combat, and eradicate the illicit trade and trafficking in small arms and light weapons (SALW), in order to combat armed violence and ease the human trafficking caused in Africa by this illicit trade of SALW (Art. 1, paras. 1, 3).

The obligations resting upon States Parties are, inter alia, to prohibit any transfer of SALW to non-state armed groups (Art. 4); to designate a national body that shall be responsible for handling issues relating to the issuance of transfer authorizations both to public institutions and to qualified private actors (Art. 5); to draw up an end-user certificate that shall be issued for all import shipment (Art. 6); to prohibit and penalize the possession, carrying, use, and trade of SALW by civilians within their respective territories (Art. 7); and to conduct semiannual inspections to evaluate and inventory stockpiles of SALW in the possession of armed and other authorized security groups and to collect, seize, register, and destroy any SALW that are surplus, obsolete, or illicit (Art. 15). In order to monitor the application of the Convention, State Parties shall support the establishment by the Economic Community of Central African States, of a group of experts responsible for follow-up and appraisal of the implementation of activities (Art. 32).

Customary humanitarian law also prohibits the use of certain types of firearms in international and non-international armed conflicts. Rule 77 of the customary IHL study states that “the use of bullets which expand or flatten easily in the human body is prohibited”; Rule 78 provides that “the anti-personnel use of bullets which explode within the human body is prohibited”; Rule 79 states that “the use of weapons the primary effect of which is to injure by fragments which are not detectable by X-rays in the human body is prohibited”; while Rule 80 states that “the use of booby-traps which are in any way attached to or associated with objects or persons entitled to special protection under international humanitarian law or with objects that are likely to attract civilians is prohibited.”

Incendiary Weapons

These weapons come under the category of firearms. Their aim is to set fire to objects or to cause burn injuries to humans. As with all weapons, it is prohibited to use them against individuals and objects protected by humanitarian law (e.g., civilians and civilian goods, including forests).

It is also prohibited to use them against combatants and military objectives that are located “within a concentration of civilians,” as per Protocol III to the 1980 Convention on Conventional Weapons (Protocol on Incendiary Weapons).

Rule 84 of the customary IHL study provides that “if incendiary weapons are used, particular care must be taken to avoid, and in any event to minimize, incidental loss of civilian life, injury to civilians and damage to civilian objects,” and Rule 85 states that “the anti-personnel use of incendiary weapons is prohibited, unless it is not feasible to use a less harmful weapon to render a person hors de combat.” Those two rules are applicable in both international and non-international armed conflicts.

Weapons of Mass Destruction

This denomination includes three categories of weapons: biological, chemical, and nuclear.

Since these are indiscriminate, by nature, their use is hard to reconcile with the spirit of humanitarian law, which is based on the military ability to distinguish between civilian and military objectives, and between civilians and members of armed forces.

Bacteriological (or Biological) Weapons

Bacteriological weapons (commonly known as biological weapons) are those that aim to spread disease that threatens the health of human beings, animals, and plants. Customary international humanitarian law prohibits the use of biological weapons in both international and non-international armed conflicts (Rule 73 of the customary IHL study). Moreover, their use, production, and stockpiling are prohibited by two main international texts:

  • the Protocol for the Prohibition of the Use of Asphyxiating, Poisonous, or Other Gases, and of Bacteriological Methods of Warfare, adopted in Geneva on 17 June 1925—this convention had 137 States Parties as of June 2015;
  • the Convention on the Prohibition of the Development, Production, and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on Their Destruction, better known as the Biological Weapons Convention (BWC), opened for signature on 10 April 1972—it had 172 States Parties as of June 2015. The fact that this Convention is relatively recent, and its prohibitions are very broad, has made it the point of reference in terms of regulating biological weapons.

The main prohibitions are enumerated in Article 1: each State Party undertakes “never in any circumstance to develop, produce, stockpile, or otherwise acquire or retain microbial or other biological agents, or toxins . . . , or weapons, equipment or means of delivery designed to use such agents or toxins.” The Convention offers no further definition, which is problematic because the meaning of “weapons, equipment or means of delivery” is now a subject of controversy among States.

The Biological Weapons Convention (BWC) entered into force in 1975; it was the first multilateral disarmament treaty banning an entire category of weapons of mass destruction. Nonetheless, the Convention has rapidly faced criticism, notably because of the fact that it lacked clear definitions of such weapons as well as a monitoring mechanism. It was only at the Third Review Conference, in 1991, that the BWC States Parties decided to investigate possible verification methods. However, this idea was abandoned in 2001, when the United States rejected a draft protocol to the Convention that would have required States Parties to declare relevant facilities and submit to inspections. In 2006, during the Sixth Review Conference, States Parties adopted a consensus regarding the creation of an Implementation Support Unit (ISU) to assist States Parties with the implementation of the Convention. The ISU is funded by the States Parties to the Convention and performs several tasks, such as administrative support and confidence-building measures and acts as a clearinghouse for assistance with national implementation. Nonetheless, the ISU has been given limited monitoring capabilities because of its size (three full-time posts), funding (funded for four years, 2007–2011), as well as mandate, as it cannot carry out inspections or enforce compliance.

The Seventh Review Conference of the BWC was been held in Geneva from 5 to 22 December 2011. It was the first opportunity for States Parties to examine the implementation of the Convention since 2006. According to the new president of the Conference, Ambassador Paul van den Ijssel of the Netherlands, it is clear that the Biological Weapons Convention needs to be strengthened by consensus. This Review Conference focused on several issues, inter alia: (a) ways and means to enhance national implementation; (b) ways to create an accountability framework to monitor compliance; (c) means to set up national, regional, and international measures to improve bio safety and bio security; (d) ways to improve confidence between States; and (e) ways to increase the ISU’s capabilities.

Chemical Weapons

Chemical weapons—the clearest definition of which is offered in the 1992 Convention listed later—cause death, temporary incapacitation, or permanent harm to humans or animals. Mainly, they include the munitions and devices that release toxic chemicals. Various conventions prohibit their use, production, and stockpiling:

  • The Hague declarations prohibiting the launching of projectiles, the aim of which is to spread asphyxiating or poisonous gases, adopted 29 July 1899.
  • The 1925 Protocol for the Prohibition of the Use of Asphyxiating, Poisonous, or Other Gases, and of Bacteriological Methods of Warfare (see above). This Convention does not include any enforcement or verification mechanisms. It prohibits the use of chemical and biological weapons in times of international conflict but does not prohibit their stockpiling or production. Furthermore, it authorizes the use of these weapons in reprisals against States that make use of such weapons first, or against States that are not parties to the Protocol.
  • The Convention on the Prohibition of the Development, Production, Stockpiling, and Use of Chemical Weapons and on Their Destruction adopted in Geneva on 3 September 1992—it entered into force on 29 April 1997 and had 190 States Parties as of June 2015. This Convention created the Organization for the Prohibition of Chemical Weapons (OPCW). Based in The Hague, this monitoring body is made up of a secretariat and teams of inspectors. It analyzes the reports that States Parties are under the obligation to submit to it concerning their activities relating to chemical agents; it carries out routine or surprise inspections to production sites; and it monitors the destruction operations of existing stockpiles.


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Customary humanitarian law also prohibits the use of chemical weapons in international and non-international armed conflicts (Rule 74 of the customary IHL study). Rule 75 specifically provides that “the use of riot-control agents as a method of warfare is prohibited,” and Rule 76 states that “the use of herbicides as a method of warfare is prohibited if they: (a) are of a nature to be prohibited chemical weapons; (b) are of a nature to be prohibited biological weapons; (c) are aimed at vegetation that is not a military objective; (d) would cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which may be expected to be excessive in relation to the concrete and direct military advantage anticipated; or (e) would cause widespread, long-term and severe damage to the natural environment.”

Nuclear Weapons

There is no general prohibition on the use of nuclear weapons. Today’s doctrine holds that nuclear weapons are weapons of mass destruction and, as such, have indiscriminate effects. From this perspective, and for both reasons, they should be prohibited by the provisions of Additional Protocol I to the Geneva Conventions that forbid indiscriminate or excessively injurious weapons (see Section I of this entry). Eight States that possess nuclear weapons have ratified Additional Protocol I with reservations of interpretation.

On 8 July 1996, the International Court of Justice (ICJ) rendered an advisory opinion on the legality of the threat or use of nuclear weapons, on the United Nations General Assembly’s request. The opinion, which is very ambiguous, reaches four main conclusions: (1) the use of nuclear weapons is neither formally prohibited nor formally authorized; (2) the threat or use of nuclear weapons is contrary to the fundamental rules of humanitarian law; (3) the use of nuclear weapons in a conflict, during actions or combats in which tactical weapons would be permitted, is strictly forbidden; and (4) it was not possible to conclude definitely whether the threat or use of nuclear weapons would be lawful or unlawful in a case of self-defense, if a State were to face an extreme circumstance that threatened its very survival.

Officially, five nuclear powers exist: the five members of the UN Security Council (China, France, the Russian Federation, the United Kingdom, and the United States). However, in 1998, both India and Pakistan conducted several nuclear tests. These two States, as well as Israel, are considered “threshold” States, meaning they have the necessary resources to produce nuclear weapons but are not officially declared as possessing them.

The International Atomic Energy Agency (IAEA), based in Vienna, Austria, monitors the use of nuclear energy, including weapons. There are two main international conventions that aim to control nuclear weapons:

  • The Treaty on the Non-Proliferation of Nuclear Weapons (known as the Nuclear Non-proliferation Treaty, or NPT), which was adopted under the aegis of the UN in 1968. It entered into force on 5 March 1970 but was suspended indefinitely in 1995. As of June 2015, it had 190 participating States, including the five Security Council nuclear powers. Israel, India, and Pakistan have not yet ratified it.
  • The Comprehensive Nuclear Test Ban Treaty (CTBT), which was adopted in 1996 at the UN Conference on Disarmament. It has not yet entered into force. It has to be ratified by forty-four nuclear-capable States, including the three threshold States, before it can enter into force. As of June 2015, 183 States had signed it, and 164 had ratified it (of which only twenty are among the nuclear-capable States, and the threshold States have declared that they will not ratify it). This treaty completes an earlier treaty, the 1963 Moscow Treaty (Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space, and under Water), which foresaw a partial prohibition on nuclear weapons.


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For details on mines, refer to the entry on ▸ Mines .

Customary humanitarian law also limits the use of landmines. Rule 81 of the customary IHL study provides that “when landmines are used, particular care must be taken to minimize their indiscriminate effects,” while Rule 83 states that “at the end of active hostilities, a party to the conflict which has used landmines must remove or otherwise render them harmless to civilians, or facilitate their removal.” Rules 81 and 83 are applicable in both international and non-international armed conflicts. Rule 82 provides that “a party to the conflict using landmines must record their placement, as far as possible” and is customarily applicable in international armed conflict and, arguably, in non-international ones.

Autonomous Combat System: Drones and Unmanned Combat Aerial Vehicle (UCAVS)

There is today a controversy regarding the legal status under international humanitarian law of unmanned aerial vehicles and drones. The debate is mainly focused on drone warfare. Although there is no treaty or customary rule prohibiting the use of autonomous attack technology, such practice raises two main questions. The first one challenges the autonomy of software in an attack decision. The second one questions the possibility to articulate this autonomous decision with the duty of distinction and precaution binding on all targeting rules (API Arts. 36, 51). The qualitative legal requirement to assess the risk for civilians and the balance between this risk and the expected military advantage cannot be left to autonomous technology and implies some form of direct human involvement, even in a remote manner. Another important element lies in the extraterritorial dimension of such attack, which take place far from the national territory of the country involved and is aggravated by the confidentiality of the agencies often operating such weapons, outside of official military command.

Toward an Arms Trade Treaty

According to the Stockholm International Peace Research Institute, based in Stockholm, Sweden, international arms trade grew by 24 percent between 1994 and 1997. In 1998, arms trade decreased slightly to $22 billion, from $25 billion in 1997.

The arms market is dominated by five exporters: the United States, the Russian Federation, France, the United Kingdom, and Germany. The main purchasing regions are Asia (39 percent of arms imports) and the Middle East (31 percent). Worldwide military and arms spending have decreased continuously since 1987, except in these two regions. In 1998, the total value of the arms market was $745 billion.

According to a report published by UN experts in August 1999, internal conflicts (which represent 90 percent of today’s conflicts) are fueled by small arms and light weapons. Five hundred million such weapons are in circulation around the world, and 40 percent of their trade is illegal, often in violation of embargoes.

In 2003, following the success of the campaign treaty on the ban of landmines, Amnesty International and Oxfam International launched the “Control Arms” campaign, which is a global civil society alliance campaigning for the drafting of an international and legally binding agreement on arms trade. In December 2006, the United Nations General Assembly adopted Resolution 61/89, in which 153 governments recognized that arms control and disarmament were essential for the maintenance of the global peace and security. Therefore, they decided to start working on the development of a global Arms Trade Treaty that would regulate the import, export, and transfer of conventional arms. In January 2009, the UN General Assembly adopted Resolution 63/240, which launched a time frame for the negotiation of the Arms Trade Treaty. This included one preparatory meeting in 2010, two in 2011, and one in July 2012 before the final negotiating conference scheduled for March 2013. At the end of this Final UN Conference on the Arms Trade Treaty, States failed to reach an agreement. The Treaty was therefore submitted to States by votes at the General Assembly. The resolution containing the text of the treaty was finally adopted on 2 April 2013 with 154 votes in favor, three against (Democratic People’s Republic of Korea, Iran, and Syria), and twenty-three abstentions. The treaty is opened to ratification since 3 June 2013 and will enter into force ninety days after its fiftieth ratification.

The Arms Trade Treaty shall be a comprehensive, legally binding instrument establishing common international standards for the import, export, and transfer of conventional arms. The goal of such a treaty is to set up a firm and transparent international mechanism to prevent and prohibit the diversion of conventional weapons and ammunition from the legal to the illicit market, where they can be used for terrorist acts, organized crime, and other criminal activities.

AttacksInternational humanitarian lawMethods (and means) of warfareMinesWar

For Additional Information: Amnesty International. Contrôler les armes . Paris: Editions Autrement, 2011.

Aubert, Maurice. “The International Red Cross and the Problem of Excessively Injurious or Indiscriminate Weapons.” International Review of the Red Cross 279 (November–December 1990): 447–97.

Boothby, W. H. “Autonomous Systems: Precautions in Attacks.” 34th Round Table on International Humanitarian Law and New Weapon Technologies. International Institute of Humanitarian Law. San Remo, 8–11 September 2011, pp. 119–33.

Coupland, Robin, and Dominique Loye. “International Assistance for Victims of Use of Nuclear, Radiological, Biological and Chemical Weapons: Time for a Reality Check?” International Review of the Red Cross 874 (June 2009): 329–40.

Dinstein, Yoram. The Conduct of Hostilities under the Law of International Armed Conflict . Cambridge: Cambridge University Press, 2004.

“A Guide to the Legal Review of New Weapons, Means and Methods of Warfare: Measures to Implement Article 36 of Additional Protocol I of 1977.” International Review of the Red Cross 864 (December 2006): 931–956.

International Institute of Humanitarian Law. XXXIV Round Table on International Humanitarian Law and New Weapon Technologies. San Remo, 8–11 September 2011.

Lawand, Kathleen. “Reviewing the Legality of New Weapons, Means and Methods of Warfare.” International Review of the Red Cross 864 (December 2006): 925–30.

Mulinen, Frederic de. Handbook on the Law of War for Armed Forces . Geneva: ICRC, 1989, appendix 1.

Oeter, Stefan. “Methods and Means of Combat.” In The Handbook of Humanitarian Law in Armed Conflicts , edited by Dieter Fleck, 121–52. Oxford: Oxford University Press, 1995.

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