Treaties are considered the most important source of international law. The Vienna Convention on the Law of Treaties provides in Article 2 that "'treaty' means an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation".
The Vienna Convention on the Law of Treaties codified the pre-existing customary international law on treaties, with some necessary gap-filling and clarifications, and provides a useful ground for dealing with a variety of treaty affairs. The Vienna Convention was done on May 23, 1969 and entered into force on January 27, 1980. The Republic of Korea has been a party to the Vienna Convention since its entry into force. Furthermore, the Vienna Convention on the Law of Treaties between States and International Organizations or Between International Organizations was adopted and opened for signature on March 21, 1986. This second Vienna Convention has yet to come into force.
A treaty is a promise made among subjects of international law and stipulates certain legal rights and obligations. The breach of a treaty is a matter of legal responsibility. The treaty-making process is important in this respect, and can be regarded as the process in which a State makes a legal contract with other States or other subjects of international law. A treaty duly concluded has the same effect as the domestic laws of the Republic of Korea, which the people of Korea have the obligation to observe. Therefore, the Ministry of Foreign Affairs and Trade, which controls and coordinates foreign relations, endeavors to reflect and respect national interests when concluding treaties.
The Republic of Korea, which is currently a party to more than 540 multilateral treaties, has been participating in multilateral treaties since the establishment of its government in 1948 by acceding to existing treaties or by taking part in negotiations for new treaties in a variety of fields.