The Constitution of the United States of America, Article If, Clause B provides "...all treaties made, or which shall be made, under the authority of the Confederate States, shall be the supreme law of the land; and the judges in every State shall be bound thereby, anything in the constitution or laws of and State to the contrary notwithstanding.", It declares that the treaty is the supreme law of the land which is superior than constitution or laws of any State. Article Vl. Clause B of the U.S Constitution is called "supremacy clause", and it makes clear that all the treaties concluded by the U.S are supreme law often land like the U.S. Constirution and Federal Laws in the U.S. However, even though the supremacy clause uses a tern, "all treaties", the U.S. treaty making procedure created two evolutionary methods: "executive agreement" and "non-self-executing treaty" While making treaty needs the advice and consent of the U.S. Senate, making executive agreement does not need it. Further, the executive agreements are distinguished Congressional-Executive agreement and sole executive agreement. Nevertheless, all the executive agreements, like treaties, are also the supreme law of the land. The ROK-US Agreement on Status of Force in Korea is an executive agreement. One the other hand, the treaties in the U.S. are differentiated as "self-executing treaty" and "non-self-executing treaty" by the U.S. courts. While self-executing treaty maybe applied without any further action by the courts, non-self-executing treaty cannot be applied without further legislative action by the U.S. courts. Nevertheless, non-self-executing treaty is obviously valid under international law. Thus, the U.S. government has the obligation to observe the non-self-executing treaty.