Many renewable resources, such as sh stocks, water or environmental quality, are shared between di erent countries. The management of such resources then relies on international agreements. We develop a model of a shared renewable resource for which there is an international agreement that determines each country's share of total extractions. Each government is responsible for the enforcement of their national quota. The countries can cheat on the agreement by reducing enforcement e orts and there by inducing their rms to violate their quotas. We analyze the e ects of this in a di ferential game framework. There are two games. First, a Stackelberg game between the government and the rms within each country. Second, an enforcement game at the international level between di erent governments. Our results suggest that no free-riding only occurs if countries have asymmetric beliefs regarding the environmental preferences of rival countries. The extent of free-riding in enforcement can be in uenced by both domestic and international policy instruments. The e ctiveness of domestic instruments (legislation) versus international instruments (treaties) depends to a large extent on resource dynamics and the countries' preferences for sustainability.
