Global environmental governance rests on a set of norms best characterized by the label “liberal environmentalism.” The 1992 Earth Summit catalyzed the process of institutionalizing these norms, which predicate environmental pro tection on the promotion and maintenance of a liberal economic order. To support this claim, this article identifies the specific norms institutionalized since Rio that undergird international environmental treaties, policies and programs. It also explains why a shift toward liberal environmentalism occurred from earlier, very different, bases of environmental governance. The implications of this shift are then outlined, with examples drawn from responses to climate change, forest protection and use, and biosafety. The article is not an endorsement of liberal environmentalism. Rather, it shows that institutions that have developed in response to global environmental problems support particular kinds of values and goals, with important implications for the constraints and opportunities to combat the world's most serious environmental problems.