Chapter I of the United Nations Charter lays out the purposes and principles of the United Nations organization. These principles include the equality and self-determination of nations and the obligation of member countries to obey the Charter, to cooperate with the UN Security Council and to use peaceful means to resolve conflicts.
Article 2, clauses 3-4 essentially prohibit war (except in self-defense) by stating, "All Members shall settle their international disputes by peaceful means in such a manner that international peace and security, and justice, are not endangered. 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 other manner inconsistent with the Purposes of the United Nations." (The right to self-defense is reaffirmed in Article 51, which states, "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 . . ."
Article 2, clause 7 of this chapter reemphasizes the fact that only the UN Security Council has the power to force any country to do anything by stating that "Nothing contained in the present Charter shall authorize the United Nations to intervene in matters which are essentially within the domestic jurisdiction of any state or shall require the Members to submit such matters to settlement under the present Charter; but this principle shall not prejudice the application of enforcement measures under Chapter VII." (Only the Security Council can institute Chapter VII enforcement measures.)