How do domestic political institutions, specifically veto players, mediate the effect of trade competition on regulatory races in the environmental area? Is the mediating effect more pronounced for more visible pollution issues such as air pollution in relation to less visible water pollution? Governments are expected to respond to trade pressures by lowering regulatory costs. To do so, governments can rewrite regulations (de jure policy change) and/or lower the enforcement of existing regulations (de facto policy change). In contrast with de facto changes, de jure policy changes are more likely to invite opposition from pro-environment constituencies, and are therefore politically more difficult. Our analysis of 140 countries for the period 1980–2003 suggests that in response to trade pressures, governments do not lower regulatory stringency by rewriting (de jure) environmental regulations for any level of domestic constraints. In contrast, when political constraints are low, governments respond to trade pressures by adjusting regulatory stringency via de facto changes. Moreover, in the context of de facto policy changes, the constraining effect of veto players is more pronounced for air pollution (sulphur dioxide) in comparison to water pollution (biochemical oxygen demand). This is because air pollution is a more visible pollution issue around which organized, urban constituencies tend to mobilize.