The article examines international law in relation to international trade in endangered species. It analyzes the major international agreement in this area: CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora 1973) in the context of Thailand and China. The article argues that CITES does not sufficiently address the need of those countries to criminalize illegal trade in endangered animals and plants across borders. CITES requires an increased administrative control over the trade which many developing countries are unable to carry out in order to achieve an effective level of protection for the endangered species. Under the influence of CITES, the crime of illegal trade is defined in Thailand and China narrowly as trade in violation of administrative controls. The main argument of this article is, first, that the countries, such as Thailand and China, must adopt a broader concept of the crime of illegal trade in endangered species. Second, there is a need to adopt this concept on an international level in order to facilitate a successful fulfillment of the countries’ international obligations.