The United Nations Charter obligates member states to settle their disputes by peaceful means, in such a manner that international peace and security and justice are not endangered. They are to refrain from the threath or use of force against any state, and may bring any dispute before the Security Council.
The Security Council is the United Nations organ with primary responsability for maintaining peace and security. Under the Charter, member states are obliged to accept and carry out its decisions. It is the only UN body whose decisions have the mandatory force for all member states.Under Chapter VII of the Charter, the Council is empowered to take measures to enforce its decisions. It can impose embargoes and sanctions, or authorize the use of force to ensure that mandates are fulfilled. However, the Council takes such action only as a last resort, when peaceful means of setling a dispute have been exhausted, and after determining that a threath to the peace, a breach of the peace or an act of aggression exists.
A very common measure to prevent or stop aggression are economic sanctions. A more formal and procedural competence of the Security Council are the recommendations to the General Assembly for the election of a Secretary General and the election of the judges of the international court of justice. The Security Council can also create special committees in order to guarantee the implementation of its decisions and resolutions (e.g. the Counter Terrorism Committee, the Tribunal for Rwanda).
The main problem for the Security Council from 1945 until the end of the Soviet Union was its inability to act, resulting from the fact that major decisions, which need 9 affirmative votes, including the ones of the 5 permanent members, were constantly vetoed by either the Soviet Union or the USA. This impasse situation could partly be bypassed by the delegation of the collective security task to the General Assembly which is able to deploy peace keeping missions. Only with the end of the Soviet Union did the Security Council take a more active role again, the first mission consisting of the authorization of the USA to intervene in the Iraq, which gave the legitimacy to this action. The absence of such an authorization in the Second Gulf War (2003), due to the opposition of France, Russia and Germany, led to one of the major crisis of the Security Council in the post cold war era.