[...]

"The Charter of the United Nations is the treaty which forms and establishes the international organization called the United Nations. While this document is often misconstrued as a constitution it is, in fact, an agreement between states and not a compact among the individual peoples to create a government. It was signed at the United Nations Conference on International Organization in San Francisco on June 26, 1945 by 50 of the 51 original member countries (Poland, the other original member, which was not represented at the Conference, signed it later). It entered into force on October 24, 1945, after being ratified by the five founding members—the Republic of China, France, the Soviet Union, the United Kingdom, and the United States—and a majority of the other signatories. As a Charter it is a constituent treaty, and all members are bound by its articles. Furthermore, the Charter states that obligations to the United Nations prevail over all other treaty obligations. Most countries in the world have now ratified the Charter. Though one notable exception is the Holy See, which has chosen to remain a permanent observer state and therefore is not a full signatory to the Charter." Source: http://en.wikipedia.org/wiki/Charter_of_the_United_Nations