International Law

International law is the legal system that regulates the relationship between states in war and peace. It applies regardless of whether the state is democratic or totalitarian. Dictatorships such as North Korea are also bound by international law.

Unlike national law, the principle of sovereignty means that control mechanisms and sanctions to ensure that states comply with international law are often lacking. The principle of sovereignty means that all states have the right to manage their internal affairs without interference from the outside world.

International law

International law is expressed in the Geneva Conventions from 1949 and is divided into different parts. International humanitarian law, also called the laws of war, is the one that concerns nuclear weapons.

Disarmament agreements are part of international law. Disarmament agreements are for the protection of states and are primarily aimed at preventing war. International humanitarian law exists to protect both combatants and civilians in war. Examples of this are the bans on cluster munitions and landmines. Among other things, they prohibit the use of these weapons because they constitute an inhumane threat to humanity. Since 2017, there is an agreement on the prohibition of nuclear weapons.

The laws of war

One of the basic principles of the laws of war is that they regulate both the conduct of battle and the types of weapons permitted. All warfare must follow the three basic principles:

  • The principle of distinction, which means that a distinction must be made between military targets and the civilian population and its buildings.
  • The principle of proportionality, which states that the possible military gain must be proportionate to the possible civilian losses.
  • The precautionary principle, which states that means of warfare and methods of warfare must be chosen to avoid or minimize civilian casualties.

With these principles as a background, the Red Cross and Red Crescent considers that nuclear weapons are not compatible with international humanitarian law. The Red Cross and Red Crescent has a special mandate to interpret, protect and develop humanitarian law.

International Court of Justice in The Hague

The question of whether nuclear weapons can be illegal has been examined by the International Court of Justice in The Hague (ICJ). The request came from the UN General Assembly and concerned whether the use of nuclear weapons is against international law. It resulted in an advisory opinion in 1996, in which the court stated that the use of nuclear weapons is generally contrary to the rules and principles of humanitarian law.

International law prohibits states from using violence against each other. Therefore, it is illegal to, for example, start a war. There is an exception in the international law prohibition for states to use force against each other. If a country has been attacked by another country, the country has the right to use force in self-defense.

The court could not rule out that there may be an extreme situation where the existence of a country is threatened, and when nuclear weapons may be used in self-defense. However, even in such a situation, the use of nuclear weapons must not lead to death or extensive damage to civilians, or affect neutral states. The court could not identify how this would happen, but could not rule out with certainty that the situation could arise. However, the court stated that nuclear weapons are generally to be considered illegal.

The International Court of Justice further stated in its advisory decision that the nuclear-weapon states party to the Non-Proliferation Treaty (NPT) have an obligation to negotiate and achieve results in nuclear disarmament. The nuclear weapon states must ensure that their nuclear weapons are abolished so that humanity can live in a world free of nuclear weapons.

Sources and more information

The Geneva conventions and their Commentaries, International Committee of the Red Cross, ICRC
Working towards the elimination of nuclear weapons, 26-11-2011 Resolution, International Committee of the Red Cross, ICRC
Legality of the Threat or Use of Nuclear Weapons, International Court of Justice
International Court of Justice and its 1996 advisory opinion, Reaching Critical Will


Swedish Physicians Against Nuclear Weapons

Last updated
21 December, 2022