Abstract: A treaty only has the validity to its contracting states. Without the consent of the third states, it cannot offer them any rights nor liabilities. Such relative validity of treaty has constituted part of customary law. However, this old principle has been challenged in contemporary international law. The Stipulation of International Criminal Court extends its jurisdiction to its non-contracting states. The regulations made by European Community can be directly applied to its member states. Furthermore, the treaty of the ocean law has been amended with the participation of its non-contracting states. Whether or not the latest development of the validity of treaty to the third states is helpful to maintain international relationship and international relationship of treaty, this is a question hard to answer but to be answered.