PSIR Simplified

The rules governing the use of military force by nations are laid out in the UN Charter. The following points are significant in this regard:

1. Under normal circumstances, the use of force in relations between nations is prohibited.

Article 2(4) of the UN Charter states that member nations shall not use military force in their mutual relations, nor shall they threaten the use of force.

B. Nations may use military force against another country only for the purpose of self-defense.

According to Article 51 of the Charter, a country may use force against another solely for self-defense. This article grants every member the right to take measures for their security, either individually or collectively. Organizations like NATO have been formed under the principle of collective security derived from this article.

However, Article 51  imposes the following conditions on the use of military force in self-defense:

1. A country may use military force against another only if it has been subjected to a military attack by that country.

2. The use of military force must be limited to what is necessary for self-defense; the use of force beyond what is necessary is prohibited.

3. The Security Council must be immediately informed of any such military action taken in self-defense, and subsequent actions must be carried out in accordance with the Security Council’s directives.

Thus, nations possess the right to self-defense both individually and collectively. Collective self-defense implies that member nations may form collective organizations, such as NATO, for this purpose.

Is the US attack on Iran in February, 2026 legally justified?

An attack by the US against Iran based on the aforementioned right to self-defense is unlawful, because Iran had not previously launched an attack against the US that posed a threat to American security.

However, the United States has interpreted the right to self-defense in a distorted manner to justify its aggression. To this end, the US has propounded a new doctrine known as the doctrine of “prospective self-defense.” Under this doctrine, the US argued that it faced a potential future threat from Iran’s nuclear weapons, and thus launched an attack on Iran. However, analysts have rejected this US argument. The UN Charter permits a country to use military force against another only when an actual attack has already occurred against it; it does not cover potential future attacks.

C.Can a Country use Military Force against another on Humanitarian Grounds?

Military intervention on humanitarian grounds refers to whether or not a country can intervene militarily in another nation where genocide or widespread human rights violations are taking place.

The concept of using military force against another country on humanitarian grounds is controversial under international law. The UN Charter contains no explicit provision for such military intervention.

Rules regarding this matter are still evolving. The generally accepted rule is that a country cannot unilaterally intervene militarily against another on humanitarian grounds.

Such intervention can only be undertaken collectively in two specific situations:

1.   By the Security Council, if it concludes that the humanitarian situation in a country is so dire that it poses a threat to global peace.

2.   Based on the “Responsibility to Protect” (R2P) principle adopted by the UN General Assembly in 2005. This proposal stipulates that collective military action under United Nations supervision may be undertaken in four situations: genocide, ethnic cleansing, war crimes, and crimes against humanity.  Such collective action will be taken only by the United Nations.

However, no single country possesses the right to carry out military intervention on humanitarian grounds in any situation.