How did the United Nations Charter limit the use of armed force by states?

The UN Charter establishes a fundamental prohibition against the threat or use of force directed at the territorial integrity or political independence of any state, or in any manner inconsistent with the purposes of the United Nations. This principle, primarily codified in Article 2(4), serves as a cornerstone of modern international law regarding the use of armed force.123

Under the Charter, states are permitted to use force only in two specific scenarios:

• Self-defense: Article 51 recognizes an "inherent right" of individual or collective self-defense if an armed attack occurs against a member state. This right remains valid until the UN Security Council has taken the necessary measures to maintain international peace and security. Any such action must be necessary and proportionate to the threat.14
• Security Council Authorization: The Security Council holds primary responsibility for maintaining international peace and security. It may authorize the use of force to address threats to the peace, breaches of the peace, or acts of aggression if diplomatic or economic sanctions prove inadequate.52

While these provisions aim to prevent war, the enforcement of these norms remains challenging due to political disagreements and the veto power held by permanent Security Council members.32