For decades, general international law has recognized that international obligations can be divided into two types, i.e. bilateral obligations and multilateral obligations, according to their own legal nature. Today, multilateral obligations are furthermore divided into erga omnes obligations and erga omnes partes obligations. The former is the obligations owed to the international community as a whole and the latter is the obligations owed to a group of States for the protection of a collective interest of the group. Contrary to general international law, for a long time, WTO law has been silent regarding the legal nature of obligations imposed on their Member States. It would be easy to consider GATT obligations as bilateral, because trade is a transaction between two states ; that is to say, trade is bilateral behavior. However, WTO law is not as simple as GATT. WTO law treats not only goods but also services, intellectual property rights and other technical or sanitary matters, so that it would covers a wide range of rights and obligations. This article clarifies the legal nature of obligations accruing to Member States under the actual WTO law on the basis of general international law.