Cheat Sheet: Use of Force and International Humanitarian Law

1. Legal Framework for Use of Force

1.1 UN Charter Provisions

1.2 Exceptions to Prohibition of Force

• Self-defense (Article 51): Individual or collective response to armed attack; must be necessary, proportionate, and immediately reported to Security Council
• Security Council authorization: Under Chapter VII to maintain or restore international peace and security
• Consent of territorial state: Use of force with valid consent (not obtained by coercion)

2. Self-Defense Under International Law

2.1 Requirements for Lawful Self-Defense

2.2 Key Cases on Self-Defense

2.3 Anticipatory and Pre-emptive Self-Defense

• Anticipatory self-defense: Response to imminent threat before attack materializes; debated but some support under Caroline criteria
• Pre-emptive self-defense: Preventive strike against potential future threat; not recognized under current international law
• Bush Doctrine (2002): Claimed right to pre-emptive self-defense against emerging threats; widely rejected by international community

3. Collective Security and Humanitarian Intervention

3.1 Collective Security System

• Article 39: Security Council determines existence of threat to peace, breach of peace, or act of aggression
• Article 41: Non-forcible measures (economic sanctions, diplomatic severance, communications interruption)
• Article 42: Military enforcement action when Article 41 measures inadequate
• Regional arrangements: Chapter VIII allows regional organizations to undertake enforcement action with Security Council authorization

3.2 Humanitarian Intervention

4. Aggression Under International Law

4.1 Definition of Aggression

• UN General Assembly Resolution 3314 (1974): Defines aggression as use of armed force by state against sovereignty, territorial integrity, or political independence of another state
• Rome Statute Article 8 bis: Crime of aggression includes planning, preparation, initiation, or execution of act of aggression by person in leadership position
• Kampala Amendment (2010): Activated ICC jurisdiction over crime of aggression from 2018

4.2 Acts Constituting Aggression (Resolution 3314)

• Invasion or attack by armed forces; military occupation however temporary; annexation by use of force
• Bombardment or use of weapons against territory of another state
• Blockade of ports or coasts by armed forces
• Attack on land, sea, or air forces of another state
• Allowing territory to be used for acts of aggression against third state
• Sending armed bands, groups, irregulars, or mercenaries carrying out armed force acts of grave consequences

5. Sources and Principles of International Humanitarian Law

5.1 Key Treaties

5.2 Fundamental Principles of IHL

5.3 Common Article 3 of Geneva Conventions

• Applies to non-international armed conflicts; minimum standards binding on all parties
• Prohibits: violence to life and person; taking of hostages; outrages upon personal dignity; extrajudicial executions
• Requires: humane treatment without discrimination; wounded and sick collected and cared for
• Considered customary international law; binding on all states and non-state actors

6. Classification of Armed Conflicts

6.1 International Armed Conflicts (IAC)

• Armed conflict between two or more states regardless of reasons or intensity
• Applies: All four Geneva Conventions and Additional Protocol I
• Includes: occupation of territory even without armed resistance; wars of national liberation (Protocol I, Article 1(4))
• Threshold: Any use of armed force between states triggers application

6.2 Non-International Armed Conflicts (NIAC)

6.3 Internationalized Armed Conflicts

• NIAC becomes internationalized when foreign state intervenes in support of one party
• Nicaragua Test: foreign state exercises overall control over non-state armed group
• Both IAC and NIAC rules may apply simultaneously to different aspects

7. Protected Persons and Objects

7.1 Protected Persons

7.2 Protected Objects

• Medical units and transports: Hospitals, ambulances marked with red cross/crescent; not attacked; protection lost if used for harmful acts
• Cultural property: Buildings dedicated to religion, art, science, education, historic monuments; not targeted unless military objectives
• Objects indispensable to civilian survival: Foodstuffs, agricultural areas, drinking water installations; prohibited to attack, destroy, or render useless
• Works containing dangerous forces: Dams, dykes, nuclear electrical generating stations; protection even if military objectives if attack causes severe civilian losses
• Natural environment: Prohibition of methods causing widespread, long-term, severe environmental damage

7.3 Specially Protected Zones

• Hospital zones: Organized to protect wounded, sick, and persons not taking part in hostilities
• Neutralized zones: Areas where military operations suspended by agreement
• Demilitarized zones: Areas from which armed forces, mobile military equipment, and military installations removed
• Non-defended localities: Inhabited places near combat zone open for occupation; prohibited to attack by any means

8. Means and Methods of Warfare

8.1 Prohibited Weapons

8.2 Prohibited Methods

• Perfidy: Feigning surrender, civilian status, or protected status to kill or injure; violations include improper use of emblems
• Denial of quarter: Declaring no survivors will be taken; ordering no quarter given
• Starvation: Using starvation of civilians as method of warfare; attacking objects indispensable to civilian survival
• Terror: Acts or threats of violence primarily to spread terror among civilian population
• Shields: Using presence of civilians or protected persons to render military objectives immune from attack
• Reprisals: Against wounded, sick, shipwrecked, medical personnel, civilians, civilian objects, cultural property

8.3 Nuclear Weapons

• ICJ Advisory Opinion (1996): Threat or use of nuclear weapons generally contrary to IHL; cannot definitively conclude on legality in extreme self-defense circumstances
• Treaty on Prohibition of Nuclear Weapons (2017): Comprehensive ban on development, testing, production, possession, use; entered force 2021; not signed by nuclear-weapon states
• No specific treaty prohibition on use exists binding nuclear-weapon states; general IHL principles apply

9. Combatants and Prisoners of War

9.1 Combatant Status

9.2 Rights and Obligations of Combatants

• Combatant privilege: Right to participate directly in hostilities; immunity from prosecution for lawful acts of war
• POW status upon capture: Entitled to POW protections under Geneva Convention III
• Duty to distinguish: Must distinguish themselves from civilian population while engaged in attack or military operation preparatory to attack
• Loss of protection: Civilians lose protection against direct attack while directly participating in hostilities

9.3 Treatment of Prisoners of War

9.4 Unlawful Combatants

• Definition: Persons taking direct part in hostilities without meeting combatant criteria; not entitled to combatant or POW status
• Mercenaries: Not combatants or POWs; Article 47 Protocol I defines six cumulative criteria
• Spies: Person clandestinely gathering information in enemy-controlled territory; not entitled to POW status if captured; may be prosecuted
• Minimum protections: Article 75 Protocol I provides fundamental guarantees; Common Article 3 applies; no torture or degrading treatment

10. Protection of Civilians

10.1 General Protection

• Definition: Persons not members of armed forces; do not take direct part in hostilities
• Principle of distinction: Parties must distinguish between civilians and combatants; civilians not object of attack
• Doubt: In case of doubt whether person is civilian, must be considered civilian
• Presence of combatants: Presence of individual combatants among civilians does not deprive population of civilian character

10.2 Prohibited Acts Against Civilians

10.3 Direct Participation in Hostilities

• Effect: Civilians lose protection from direct attack for such time as they directly participate
• Three cumulative requirements: (1) threshold of harm to military operations or capacity; (2) direct causation between act and harm; (3) belligerent nexus
• Examples: Taking up arms, planting bombs, gathering tactical intelligence for immediate use, serving as human shields
• Not direct participation: Selling goods to armed forces; general political support; indirect war-sustaining activities

10.4 Occupied Territory

11. Enforcement of International Humanitarian Law

11.1 Grave Breaches of Geneva Conventions

• Definition: Serious violations against protected persons or property; trigger universal jurisdiction
• List of grave breaches: Willful killing; torture or inhuman treatment; biological experiments; extensive destruction of property not justified by military necessity; compelling service in hostile forces; willfully depriving POW/civilian of fair trial; unlawful deportation or confinement; taking hostages
• Universal jurisdiction: All states obliged to search for and prosecute or extradite perpetrators regardless of nationality or location
• No statute of limitations: Grave breaches may be prosecuted at any time

11.2 War Crimes

11.3 International Criminal Tribunals

11.4 International Criminal Court War Crimes Jurisdiction

• Article 8 Rome Statute: ICC jurisdiction over war crimes as part of plan or policy or large-scale commission
• IAC war crimes: Grave breaches of Geneva Conventions; serious violations of laws and customs of war
• NIAC war crimes: Serious violations of Common Article 3; serious violations of laws applicable to NIAC
• Preconditions: State party, Security Council referral, or ad hoc acceptance of jurisdiction
• Complementarity: ICC acts only when states unwilling or unable genuinely to investigate or prosecute

11.5 Individual Criminal Responsibility

11.6 Defenses and Immunities

• Superior orders: Not defense to war crimes if person knew order was unlawful; manifestly unlawful orders (e.g., genocide) no defense
• Head of state immunity: No immunity before international criminal tribunals for war crimes, crimes against humanity, genocide
• Official capacity: Position as government official or military commander does not relieve criminal responsibility
• Statute of limitations: War crimes and grave breaches not subject to statutory limitation

12. Implementation Mechanisms

12.1 National Implementation

• Duty to enact legislation: States must pass laws to punish grave breaches and war crimes
• Military manuals: Armed forces must incorporate IHL into training and operational manuals
• Legal advisers: States must ensure legal advisers available to advise military commanders on IHL compliance
• Dissemination: States must make Geneva Conventions known as widely as possible in peacetime and wartime
• National commissions: Many states establish national IHL committees to promote implementation

12.2 Protecting Powers and ICRC

12.3 Fact-Finding and Monitoring

• International Fact-Finding Commission: Article 90 Protocol I; permanent body to inquire into grave breaches; requires acceptance by parties; rarely activated
• UN Commissions of Inquiry: Established by Security Council, General Assembly, or Human Rights Council to investigate violations
• UN Human Rights Council: Investigates violations through special rapporteurs, commissions, fact-finding missions
• NGO monitoring: Organizations document violations; report to international bodies; advocate for accountability

12.4 State Responsibility

• Attribution: State responsible for violations by its organs, armed forces, and persons exercising governmental authority
• Obligations: Prevent violations by forces under control; investigate and prosecute perpetrators; provide reparations to victims
• Reparations: Include restitution, compensation, satisfaction, guarantees of non-repetition
• Countermeasures: Other states may adopt lawful countermeasures to ensure compliance with IHL; must be proportionate and not affect humanitarian obligations
• Nicaragua case principle: Conduct of person or group attributable to state if state exercises effective control over operations

13. Key Landmark Cases

13.1 Use of Force Cases

13.2 IHL Cases

14. Recent Developments and Contemporary Issues

14.1 Cyber Warfare

• Tallinn Manual 2.0 (2017): Expert analysis of IHL application to cyber operations; not binding but influential
• Use of force threshold: Cyber operations causing physical damage or injury can constitute use of force or armed attack
• IHL applicability: Principles of distinction, proportionality, precaution apply to cyber operations in armed conflict
• Challenges: Attribution difficulties; defining cyber attacks; dual-use infrastructure targeting

14.2 Autonomous Weapons Systems

• Definition: Weapon systems that select and engage targets without human intervention once activated
• Legal concerns: Compliance with distinction and proportionality; accountability for violations; human dignity concerns
• Martens Clause application: Until comprehensive regulation, actions governed by principles of humanity and dictates of public conscience
• CCW discussions: Ongoing intergovernmental discussions on lethal autonomous weapons systems; no consensus on regulation

14.3 Terrorism and IHL

• Relationship: IHL applies to armed conflicts; counter-terrorism operations may or may not reach armed conflict threshold
• Non-international armed conflict: Applies when hostilities with organized armed groups reach required intensity and organization
• Not armed conflict: Law enforcement paradigm applies; human rights law governs; lethal force limited to strict necessity
• Guantanamo detention: US detention post-9/11 raised questions about applicability of Geneva Convention III and proper classification of detainees
• Targeted killings: Legality depends on applicable legal framework; different rules for armed conflict vs. law enforcement

14.4 Non-State Armed Groups

• Binding effect: IHL binds non-state parties to armed conflict; Common Article 3 obligation
• Capacity: Groups can be held accountable through international criminal tribunals and domestic courts
• Agreements: Special agreements between parties encouraged to bring additional IHL provisions into force
• Engagement: Humanitarian organizations engage with armed groups to promote compliance; does not confer legitimacy

14.5 Protection of Journalists

• Status: Journalists in armed conflict zones are civilians; protected against direct attack unless directly participating in hostilities
• Article 79 Protocol I: Journalists undertaking dangerous professional missions in areas of armed conflict protected as civilians
• Targeting: Attacks on journalists constitute war crimes; deliberate killing of civilian journalists prohibited
• Accreditation: May obtain identity card from state authorities; not required for protection

14.6 Private Military and Security Companies

• Legal status: Employees are civilians unless incorporated into armed forces
• Direct participation: Lose protection from attack while directly participating in hostilities
• State responsibility: Hiring state responsible for violations by PMSC personnel under its control
• Montreux Document (2008): Non-binding guidelines on state obligations regarding PMSCs; 58 signatory states
• Accountability gaps: Challenges in prosecuting violations by PMSC personnel; jurisdictional and immunity issues