This chapter shows that a harsh ban on export duties is inconsistent with the practice of World Trade Organization (WTO) members and economic rationale in two respects. First, the actual examples of country practices and economic research show that export duties could be useful to reduce local or global pollution under certain circumstances, because the theoretically best environmental policies are not always feasible in financial or practical terms. Second, the suggestion that export duties could be substituted by export quotas lacks sound basis. The environmental regulatory autonomy with respect to export duties is always preserved for WTO members at both the multilateral and regional levels, except for the WTO ban on China’s export duties. The OECD opinion is echoed by the practice of WTO members, which shows a clear preference for export duties over quantitative restrictions.