---
title: "Use of Force: UN Charter, Self-Defence and R2P"
description: "The UN Charter bans force with only two exceptions, self-defence and Security Council authorisation; learn these rules and the contested R2P doctrine for exams."
url: "https://modeldiplomat.com/learn/lessons/exam-international-law-use-of-force-the-un-charter-self-defence-r2p"
---

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Use of force: the UN Charter, self-defence & R2P

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# Use of force: the UN Charter, self-defence & R2P

The Charter prohibition on force, its two exceptions (self-defence and Security Council authorisation), and the contested doctrine of R2P.

## The cornerstone rule

The modern *jus ad bellum* rests on **Article 2(4) of the UN Charter (1945)**: 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 manner inconsistent with the purposes of the United Nations. The International Court of Justice in *Nicaragua v. United States* (Merits, 27 June 1986) held that this prohibition is not merely treaty law but a rule of **customary international law** and a candidate for *jus cogens* — a peremptory norm from which no derogation is permitted (Articles 53 and 64, Vienna Convention on the Law of Treaties, 1969).

The Charter scheme is a near-total ban with only **two recognised exceptions**, both narrowly drawn:

1. **Individual or collective self-defence** under **Article 51**, available only "if an armed attack occurs" against a member, and only "until the Security Council has taken measures necessary to maintain international peace and security."
2. **Collective enforcement authorised by the Security Council** under **Chapter VII** (Articles 39, 41 and 42), once the Council has determined the existence of a threat to the peace, breach of the peace, or act of aggression under Article 39.

## What falls outside the exceptions

Reprisals involving force, armed intervention to protect nationals abroad, and the broad notion of "humanitarian intervention" without Council authorisation have **no settled basis** in the Charter. The 1999 NATO bombing of the Federal Republic of Yugoslavia over Kosovo proceeded without a Security Council resolution; the Independent International Commission on Kosovo (2000) famously called it "illegal but legitimate," capturing precisely the gap between law and asserted morality.

## Aggression defined

**UN General Assembly Resolution 3314 (XXIX) of 14 December 1974** offers the working **definition of aggression**, listing acts such as invasion, bombardment, blockade of ports, and the sending of armed bands. This definition was later adapted into the **crime of aggression** under **Article 8 bis of the Rome Statute**, activated for the International Criminal Court by the Kampala amendments (Assembly of States Parties, 2010; jurisdiction activated 17 July 2018).

The coherence of the Charter system was tested by the **2003 invasion of Iraq**, justified by the US and UK partly on a "revival" of Resolution 678 (1990) through Resolution 1441 (2002). UN Secretary-General Kofi Annan stated in September 2004 that, from the Charter's point of view, the war was "illegal." Candidates should retain the structure: prohibition (2(4)) + two exceptions (51 and Chapter VII) + the residual category of unlawful force dressed up as policy.

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