The Use Of Force In International Law
Introduction
International law governs when and how states may lawfully use force. The United Nations Charter and customary international law set out the legal framework on the resort to force by states. Use of force by states is prohibited, except in cases of self-defense or collective security authorized by the UN Security Council.
There are three main exceptions to the general prohibition on force: self-defense, collective security, and humanitarian intervention. The right to self-defense, outlined in Article 51 of the UN Charter, allows states to use force in response to an armed attack. Collective security is authorized by the UN Security Council under Chapter VII of the Charter. Humanitarian intervention, though controversial, may be justified under customary international law in cases of grave human rights violations.
International law has evolved to address modern threats like terrorism and civil wars. However, balancing state sovereignty and human rights remains an ongoing challenge. Overall, international law aims to restrict use of force to promote peace and security. This content will provide an overview of the key principles and complexities involved.
Use of Force by States
States may use force under international law for purposes of self-defense. The key provisions related to self-defense are found in Article 51 of the UN Charter, which states:
“Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.”
Article 51 affirms that states have an inherent right to individual or collective self-defense if they are subject to an armed attack. Self-defense actions must be reported to the UN Security Council, but states do not need to wait for Security Council authorization to act in self-defense. The Security Council retains authority and responsibility for maintaining international peace and security. Self-defense, when properly applied, provides an exception to the general prohibition on the use of force under Article 2(4) of the UN Charter.
Categories of Force
Under international law, there are three main categories of compulsion that states can use: retorsion, reprisals, and self-defense.
Retorsion
Retorsion refers to unfriendly but lawful acts by one state towards another in response to perceived wrongs. This could include economic sanctions, withdrawal of diplomatic relations, or other acts that do not involve the use of military force. Retorsion aims to impose some cost or harm on another state, without violating international law. For example, if State A commits a legal wrong against State B, State B could respond with lawful countermeasures like trade sanctions. The key is that retorsion itself does not involve legally prohibited acts.
Reprisals
Reprisals refer to acts that would be unlawful if not for the fact that they are in response to a prior unlawful act. For example, if State A illegally seizes assets owned by State B, then State B may seize assets owned by State A in reprisal. Reprisals aim to compel the other state to cease its unlawful conduct. Historic examples include seizure of goods at sea, restricted navigation rights, or even limited use of armed force. The legality of reprisals under modern international law is heavily restricted.
Self-Defense
Self-defense is the use of force by a state to protect itself from an actual or imminent armed attack. Under Article 51 of the UN Charter, states have an inherent right of individual or collective self-defense. Self-defense aims to repel an armed attack and prevent continued assaults. The criteria for lawful self-defense are discussed more below.
Self-Defense
The right to self-defense is an inherent right of states. A state’s right to defend itself is not dependent on a treaty agreement between states. Article 51 of the UN Charter recognizes that this right can be exercised individually and collectively. This means that a collection of states can use force collectively against an aggressor state, legitimized by the UN Charter. The UN Charter requires states to inform the Security Council when acting under Article 51.
Use of Force, Self Defence and Non-state actors
In order to be able to use force in self-defence, a state has to be able to demonstrate that it has been the victim of an armed attack from another state. This requirement comes from the Caroline case, a 19th century dispute between the United Kingdom and the United States.
The Caroline case established that there must be a “necessity of self-defence, instant, overwhelming, leaving no choice of means, and no moment of deliberation” for a state to justify using force in self-defence. The Caroline case set a high bar for self-defence claims. A state cannot use force against non-state actors within another state unless the attacks from those non-state actors are equivalent to an armed attack from that state.
This means that for a state to claim self-defence against a non-state actor like a terrorist group located in another state’s territory, the attacks from that group must be very severe. The state harboring the non-state actor must also be unwilling or unable to deal with the non-state actor themselves for the use of force to potentially be justified under self-defence. The Caroline case established strict limits on using force in self-defence that still influence international law today.
Humanitarian Intervention and Responsibility to Protect
The issue of intervention by the United Nations in situations of extreme humanitarian need has evolved in recent decades. In 1991, the UN Security Council authorized intervention in Iraq based on the customary international law principle of humanitarian intervention in extreme cases. This intervention was triggered by Saddam Hussein’s widespread repression of the Kurdish and Shia populations in Iraq. The Security Council condemned these actions in Resolution 688 and authorized member states to take measures to protect the populace. This lead to the United States, United Kingdom, and France proclaiming ‘no-fly zones’ in the north and south of Iraq to protect civilians from air attacks by the Hussein regime. This set an important precedent for UN-sanctioned humanitarian intervention that helped shape the later development of the Responsibility to Protect doctrine.
The UN Charter
Article 2(4) of the United Nations Charter prohibits the threat or use of force by states against the territorial integrity or political independence of any state. This prohibition is a cornerstone of the UN system and modern international law governing relations between states.
Article 2(4) specifically states:
All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.
This clause provides a broad prohibition on the use of force, covering any kind of force used unlawfully and without justification against another state. It aims to prevent aggression and conflict between states. The only exceptions to Article 2(4) are self-defense under Article 51 and collective security actions authorized by the UN Security Council under Chapter VII of the Charter.
The prohibition on the use of force reinforces the concept of sovereign equality of states and non-intervention in domestic affairs that form the basis of international law. By accepting the UN Charter, member states agree to refrain from unilateral use of force and only use military action within the UN framework. This promotes peaceful dispute resolution and collective responses to threats to peace and security.
International Law and Civil Wars
International law generally treats civil wars as purely internal matters of the state involved, with the possible exception of civil conflicts related to self-determination. The international legal framework applies different rules to civil wars depending on how third-party states categorize and recognize the warring factions.
For example, if third-party states recognize the rebel group as lawful belligerents, then the civil war is treated as an international armed conflict under international humanitarian law. This allows the rebel group certain rights such as prisoner of war status if captured.
However, if third-party states consider the rebel group as insurgents rather than lawful belligerents, then the conflict remains an internal matter. International law imposes more limits on third-party involvement and rebel rights in internal conflicts.
A key exception is self-determination conflicts, where a group within a state is fighting for independence or greater autonomy. International law has increasingly recognized a right to self-determination, which can legitimize certain civil conflicts as more than purely internal matters. However, the exact scope of the self-determination exception remains debated.
Overall, categorization of the conflict and recognition of the parties involved plays a key role in determining how international law treats civil war situations. Absent issues of self-determination, civil wars tend to be regulated as internal matters between a state and insurgents.
Terrorism and International Law
Various UN conventions and resolutions have addressed terrorism under international law over the decades.
In December 1972, the General Assembly established an Ad Hoc Committee on Terrorism. In 1994, the UN adopted a Declaration on Measures to Eliminate International Terrorism (Malcolm, p. 1160).
Key conventions adopted include:
- 1997: International Convention for the Suppression of Terrorist Bombing
- 1999: International Convention for the Suppression of the Financing of Terrorism
- 2005: International Convention for the Suppression of Acts of Nuclear Terrorism
In September 2006, the UN General Assembly adopted the United Nations Global Counter-Terrorism Strategy. This strategy condemned terrorism as a threat to international peace and security. It called for:
- International cooperation on counter-terrorism
- Addressing conditions conducive to terrorism
- Preventing and combating terrorism
- Building state capacity to prevent terrorism
- Ensuring respect for human rights and rule of law while fighting terrorism
The UN has clearly condemned terrorism and taken steps to coordinate international efforts to combat it within a human rights framework.
Conclusion
The issue of the use of force under international law is complex, with competing principles often coming into tension. On the one hand, the UN Charter prohibits the threat or use of force, emphasizing territorial integrity, sovereignty, and non-intervention. On the other hand, states retain an inherent right to self-defense, individually and collectively, in the face of an armed attack.
Customary international law has also recognized humanitarian intervention in extreme cases, though the legality remains controversial. When civil wars arise, international law treats them as internal matters, unless they involve self-determination or foreign intervention. More recently, terrorism has become a major concern, prompting additional treaties and UN strategies aimed at suppression and prevention. However, balancing security and human rights continues to pose challenges.
While international law places limits on the recourse to force, its precise boundaries remain subject to interpretation and politics. This content has surveyed key principles, cases, and developments regarding the international legal framework on the use of force and armed conflicts between and within states. The complexities reflect an evolving attempt to restrict war and violence while maintaining state security.