Necessity and Proportionality in International Humanitarian Law: Legal Boundaries in Armed Conflict

Introduction

The Principles of Necessity and Proportionality are the foundation of legal boundaries and fundamental tenets of International Humanitarian Law (IHL). The rules of IHL govern the conduct of hostilities by limiting the means and methods of warfare. These rules create a balance between military action and the principle of humanity. Necessity and Proportionality are such two principles designed to limit death and destruction during war.  They exist at all levels of international and domestic law and have an implied obligation of assessment during an armed conflict.

The Principle of Necessity, also known as Military Necessity[1], is a concept used to justify the use of armed force. The principle dictates that the use of force must be absolutely required to achieve a ‘legitimate military objective’, ensuring that the force used is essential. This standard rule of war limits military actions to necessary applications, prohibiting the use of force beyond the necessary target.

The Principle of Proportionality[2] is the second pillar of International Humanitarian Law, as articulated in Article 51(5)(b) of Additional Protocol 1.[3] This principle legitimizes military actions by determining the balance between objectives, means, and methods employed, alongside the consequences of using armed force. It is related to the principles of precaution and distinction, establishing a core responsibility for military commanders. Additionally, this principle serves as a tool in criminal law, as it may lead to individual criminal responsibility for potential war crimes and crimes against humanity.

These two principles are a crucial part of jus in bello, governing the right conduct of war. They reflect a commitment to humanitarian values, which is highly imperative for modern armed conflicts. There is a distinction between the nature of methods and means of warfare today and what it was during World War II. Learning from the history and vast evidence of the harrowing consequences of wars, the principles of necessity and proportionality are essential to maintaining a moral and legal framework to guide military conduct while safeguarding humanitarian considerations.

Legal Foundations of Necessity and Proportionality in IHL

The legal foundation of necessity and proportionality is primarily based on the Geneva Conventions, their Additional Protocols, and customary international law. They ensure an equilibrium between military objectives and humanitarian imperatives. Civilian suffering during a war cannot completely cease but can be minimised.

The Geneva Conventions of 1949 and their Additional Protocols (1977) explicitly refer to the principles of necessity and proportionality. The Additional Protocol 1 (Article 51(5)(b)) prohibits “indiscriminate attacks” and states that collateral damage should not be excessive as a consequence of achieving a military objective.

Article 57 (2)(a)(iii) of Additional Protocol reinforces the need for proportionality in military objectives by stating, “refrain from deciding to launch any attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated”[4] Such provisions create an obligation for the military commander to assess the impact on civilians against the anticipated military gain before the attack is executed.

Beyond treaties, these principles are integral elements of customary international humanitarian law. Their customary status means that these principles are binding on all states, regardless of whether they are members of specific treaties. The International Committee of the Red Cross has affirmed that these principles are universally recognized and apply to both international and non-international armed conflicts.

The Martens Clause[5] further safeguards civilians, though it does not explicitly state the principles. Nevertheless, the clause asserts that if certain legal provisions are absent during wartime, civilians should be treated humanely and protected from unnecessary suffering. This clause complements existing principles and establishes a humanitarian obligation that transcends statutory law. The legal foundation of proportionality and necessity is rooted in the foundation of IHL in both treaty and customary sources. Along with the Martens clause, a comprehensive framework is established that protects civilians while allowing for necessary military actions.

Principle of Necessity in Armed Conflict

The Principle of Necessity, also referred to as military necessity, allows for military actions that are essential for achieving specific goals during war while keeping the actions bound to IHL. However, this principle cannot be used to justify war crimes or any other action that violates humanitarian law. The concept of necessity means the action must directly contribute to defeating the targeted enemy without causing unnecessary suffering and destruction.[6] The principle is primarily based on four main elements:

1. Military action should be urgent
2. Necessary to achieve
3. Known military purpose
4. Consistent with international humanitarian law

In situations where the Geneva Convention is breached and alleged war crimes and/or crimes against humanity are committed, establishing the absence of any military necessity becomes of the utmost importance for the prosecutor. Necessity does not stand as an isolated principle. It must always be articulated with other rules of warfare. Asserting military necessity is not sufficient, which is why proportionality, precaution and distinction are interrelated.

The International Court of Justice (ICJ) Advisory Opinion on the Legality of the Use or Threat of Nuclear Weapons (1996)[7] is a significant case that highlights the complexities of military necessity. The ICJ provided legal guidance and clarification as a formal advisory response to the United Nations General Assembly. The court concluded that while states have a right to self-defence, the use or threat of nuclear weapons would be contrary to international and humanitarian law. The court stated that it could not definitively state whether the use of nuclear weapons would be lawful as they can create catastrophic consequences. ICJ found that under Article VI of the Nuclear Non-Proliferation Treaty[8] and other international laws, states have an obligation to "pursue in good faith and bring to a conclusion negotiations leading to nuclear disarmament in all its aspects under strict and effective international control".[9] The court did not make a new law but rather confirmed a well-established principle of war.

Principle of Proportionality in Armed Conflict

The Principle of Proportionality in armed conflict states that the civilian harm caused by a military should be proportionate.[10] The principle requires that the effect of military means and methods must not be disproportionate to the military advantage. It seeks to limit the damage caused by military operations to civilians and civilian objects. The application of this principle is critical for the modern warfare climate as it has advanced to airstrikes, drone warfare, siege warfare, and targeted killing which increases the potential loss of civilian casualties.

The principle is specific to situations of attacks against military objectives when collateral damage is expected. The application of proportionality lacks breadth, suggesting it is rather a rule and not a principle. However, determining whether the loss is proportionate to the military advantage is subjective, raising the question, “How to assess the value of innocent human lives as opposed to capturing or destroying a particular military objective?”[11] In situations where there is doubt regarding the legality of the application, the court may assess the proportionality of facts as a posteriori,[12] meaning that the court will evaluate the legality after the fact based on available evidence.

In 1999, NATO intervened in Kosovo, aiming to halt the human rights abuses against Albanians by Serbian forces during the war. The NATO military campaign was justified under humanitarian necessity and stated that military action was required to prevent atrocities.[13] Nevertheless, NATO was criticised for airstrikes that targeted civilian infrastructure, which resulted in excessive civilian casualties and damage. The Chinese embassy bombing in Belgrade further raised questions and accusations regarding negligence of proportionality.

The International Criminal Tribunal for the Formal Yugoslavia (ICTY) analysed these allegations under the framework of IHL. The tribunals emphasised that while military necessity can be exercised and used to justify certain actions, it does not absolve the parties from following proportionality.[14]

Conclusion

In conclusion, proportionality and necessity are fundamental to IHL and the protection of civilians. They ensure that military operations are conducted within the ambit of the boundary established by them. However, the effectiveness of the application can be challenging as excessive casualties can be subjective specifically during modern warfare.

Some might argue that there is an urgent need for stronger mechanisms. However, parties can create loopholes as there are limitations to international law. As the nature of conflicts evolves, the only effective measure can be domesticating international principles into law and policy and having a course of action for the violation of such laws. It is imperative to ensure the principles remain relevant and effective by strengthening legal frameworks and fostering international cooperation. 

[1] ICRC, ‘Military Necessity’ (ICRC Casebook) https://casebook.icrc.org/a_to_z/glossary/military-necessity.

[2] ICRC, ‘Proportionality’ (ICRC Casebook)  https://casebook.icrc.org/glossary/proportionality

[3] Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I) (adopted 8 June 1977) art 51 https://ihl-databases.icrc.org/en/ihl-treaties/api-1977/article-51. accessed 19^th February 2025

[4] Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I) (adopted 8 June 1977) art 57 https://ihl-databases.icrc.org/en/ihl-treaties/api-1977/article-57  accessed 19^th February 2025

[5] Rupert Ticehurst, ‘The Martens Clause and the Laws of Armed Conflict’ (International Institute of Humanitarian Law, July 2021) https://www.onlinelibrary.iihl.org/wp-content/uploads/2021/07/Martens-Clause-LOAC.pdf  accessed 19^th February 2025

[6] Military Necessity’ in The Practical Guide to Humanitarian Law https://guide-humanitarian-law.org/content/article/3/military-necessity/  accessed 19^th February 2025

[7] Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) [1996] ICJ Rep 226 https://www.icj-cij.org/case/95    accessed 19^th February 2025

[8] Treaty on the Non-Proliferation of Nuclear Weapons (adopted 1 July 1968, entered into force 5 March 1970) 729 UNTS 161 https://www.un.org/en/conf/npt/2005/npttreaty.html  accessed 19^th February 2025

[9] Reaching Critical Will, ‘International Court of Justice and its 1996 Advisory Opinion’ https://www.reachingcriticalwill.org/resources/fact-sheets/critical-issues/4744-international-court-of-justice-and-its-1996-advisory-opinion   accessed 19^th February 2025

[10] Mishal Murad, ‘Cardinal Principles of International Humanitarian Law’ (12 August 2021) DLP Forum https://www.dlpforum.org/2021/08/12/cardinal-principles-of-ihl/  accessed 19^th February 2025

[11] William J Fenrick, ‘Applying IHL Targeting Rules to Practical Situations: Proportionality and Military Objectives’ Windsor Yearbook of Access to Justice https://wyaj.uwindsor.ca/index.php/wyaj/article/view/4535  accessed 19^th February 2025

[12] ‘Proportionality’ in The Practical Guide to Humanitarian Law https://guide-humanitarian-law.org/content/article/3/proportionality/  accessed 19^th February 2025

[13] NATO, ‘Kosovo Air Campaign (March-June 1999): Operation Allied Force’ https://www.nato.int/cps/en/natohq/topics_49602.htm#:~:text=In%201999%2C%20once%20all%20diplomatic,a%20total%20of%2078%20days  accessed 19^th February 2025

[14] ICTY, ‘Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia’ (2000) https://www.icty.org/en/press/final-report-prosecutor-committee-established-review-nato-bombing-campaign-against-federal  accessed 19^th February 2025

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