The author sets out a realist defense of the claim that in the absence of an international enforcement agency, multinational corporations operating in a competitive international environment cannot be said to have a moral obligation to contribute to the international common good, provided that interactions are nonrepetitive and provided effective signals of agent reliability are not possible. Examples of international common goods that meet these conditions are support of the global ozone layer and avoidance of the global greenhouse effect. Pointing (...) out that the conclusion that multinationals have no moral obligations in these areas is deplorable, the author urges the establishment of an international enforcement agency. (shrink)