law of armed conflict


United Nations Charter Chapter 1 Article 2 sub 4: “All members shall refrain in 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.”

UN Charter can be found here:

When can force be lawfully used?

The body of law concerned with the justification to engage in war is known as jus ad bellum. There are two circumstances, as outlined in the UN Charter:

  • 1. The United Nations Security Council authorise the use of force as determined in Chapter VII:

Article 39: The UN Security Council shall determine the existence of a threat to the peace.

Article 41: The UN Security Council may decide what measures not involving the use of force are to be employed.

Article 42: If Article 41 is inadequate, Article 42 states that the UN Security Council may take action involving the use of force by air, sea or land to maintain or restore international peace and security.

Article 43: All members of the United Nations agree to make available to the Security Council armed forces, assistance and facilities necessary for maintaining international peace and security. Agreements and arrangements should govern the numbers and types of forces, level of readiness and nature of assistance and facilities available.

Article 47: There shall be an established Military Staff Committee to advise and assist the UN Security Council on all questions relating the employment and command of forces.

  • 2. The right to self-defence. This is made clear in Article 51, Chapter VII of the UN Charter: “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”

There are some who claim a third circumstance for force can be lawfully used, namely a humanitarian intervention, but this has no legal basis unless the humanitarian intervention is authorised by the UN Security Council as determined by Chapter VII of the UN Charter.

If force is used, what laws are involved?

The law of armed conflict is known as jus in bello.

1. Treaties (or conventions)

Includes the Geneva Conventions, The Hague Conventions (1899 and 1907), The Universal Declaration of Human Rights (1948), UN Charter (1945), Genocide Convention (1948), United Nations Convention Against Torture (1984), Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects (1980), the Chemical Weapons Convention (1992), the Convention on the Physical Protection of Nuclear Material (1980).

2. Customary international law

Not all the laws of armed conflict is covered by treaties, and treaties are not signed and ratified by all states in the world. This shows the importance of custom governing the conduct of parties. International custom is one of the four main sources of international law identified in Article 38 of the Statute of the International Court of Justice. Customary international law is based on unwritten rules that is binding on all states, based on assumed consent evidenced by the behaviour of states, and a belief by states that it is a legal obligation (opinio juris).

This is reaffirmed in Article 1 (2) of Additional Protocol I of the Geneva Conventions “Civilians and combatants remain under the protection and authority of the principles of international law derived from established custom from the principles of humanity and from the dictates of public conscience.”

Why have laws on the use of force?

  • Protect both combatants and non-combatants from unnecessary suffering.
  • Protect fundamental human rights of persons during armed conflict, especially prisoners of war, wounded and the sick, and civilians.
  • Facilitate the restoration of peace.

Principles behind the laws of armed conflict:

  • Armed conflict should not cause unnecessary destruction, and should be limited to the purposes that started the war (e.g political goals, territorial control)
  • Wars should come to an end as quickly as possible.
  • Non-combatants and their property should be protected against suffering and destruction.

What happens if states or individuals break the laws of armed conflict?

  • States that have not signed the Third and Fourth Geneva Conventions are not protected by them.
  • Persons who commit war crimes may be held accountable. This can be in domestic courts or international courts and tribunals such as the International Criminal Court.
  • The signing of treaties (or conventions) implies states will adhere to the laws of armed conflict in good faith. Good faith is considered part of the general principles of law recognised by civilised nations.