Under Chapter VII, Article 41 of the UN Charter the Security Council may impose enforcement measures in order to maintain or restore international peace and security. Such measures include economic sanctions:  

"The Security Council may decide what measures not involving the use of armed force are to be employed to give effect to its decisions, and it may call upon the Members of the United Nations to apply such measures. These may include complete or partial interruption of economic relations and of rail, sea, air, postal, telegraphic, radio, and other means of communication, and the severance of diplomatic relations." 

In accordance with the resolutions imposing sanctions the Security Council has established sanctions committees to supervise the implementation of these decisions.