Chapter 9 – Use of Force

Principles of the Law on Use of Force

• Military Necessity: Using force only when required to achieve a legitimate military objective.

• Caroline Test: Defines conditions for self-defense as "necessity" being immediate, overwhelming, and leaving no alternative.

• Proportionality: Ensuring the force used is appropriate to the threat and not excessive.

Evolution of Law

• Hague Law: Early international agreements regulating war conduct.

• 1928 Pact of Paris (Kellogg-Briand Pact): Renounced war as a tool of national policy.

• 1945 UN Charter: Core framework governing use of force in international relations.

• Article 2(4): Prohibits the use of force except in specific exceptions.

• Article 51: Recognizes the right to self-defense in response to an armed attack.

• Permissive v. Restrictive Readings

  • Permissive: Allows broader interpretations of self-defense and intervention.

  • Restrictive: Limits force strictly to self-defense or Security Council authorization.

Customary International Law of Interventions

Exceptions

• Security Council Authorization

  • Explicit: Direct approval of force.

  • Implicit: Actions tacitly supported by the Council.

• Self-Defense

  • Armed Attack: Must meet the gravity threshold to justify force.

  • Preemptive Self-Defense: Controversial and debated in legality.

• Other Potential Exceptions

  • Protecting Nationals

  • Humanitarian Intervention and the Responsibility to Protect

  • Consent- Use of force is lawful with the host state's permission