Illegal extractions of renewable resources threaten sustainable use of those resources. The world community has recently paid increasing attention to the issue of illegal logging. This paper tries to explain why it is important to exclude illegally logged timber from the international market by using a stylized model in the literature of trade and renewable resources. It is shown that a fall in the price of timber may cause a switch of management regime from enforced property rights to open-access, expanding the supply of timber and reducing forest stock. When several countries export timber, an increase in illegal logging in one country due to a regime switch may also increase illegal logging in other countries. While conflicting with the GATT/WTO rules for reasons of discrimination by process and production methods (PPMs), import restrictions only on illegally logged timber will be effective to prevent the international diffusion of illegal logging.