This article provides ethnographic insights into the making of the latest UN-backed instrument for transnational environmental law and governance: the Global Pact for the Environment (GPE). It narrates the rise and fall of a contemporary policy project designed to unify and strengthen international environmental law. The story starts in 2015 on the premises of a Parisian legal think tank and ends in May 2019 at the headquarters of the United Nations Environment Programme in Nairobi, where states ultimately decided not to adopt the GPE as a legally binding instrument but opted to prepare a political declaration to be presented in 2022 at the occasion of the 50th anniversary of the UN Conference on the Human Environment. The time between 2015 and 2019 is divided in two periods. From 2015 to 2017, the GPE was imagined, drafted, and promoted by a group of non-state actors mainly constituted by legal academics. From 2017 to 2019, the GPE was introduced in the UN machinery and turned into a state-oriented policy process. Based on original interview material and an unexplored archive of primary sources, the article traces the multiplicity of actants enrolled in the GPE, the interests that held them together, and the institutional ties they built for the project to materialize. It draws on actor-network theory's model of translation—through problematization, interessement, enrolment, and mobilization—to reassemble the bonds between human and nonhuman actants in the making of the “global,” the “pact,” and the “environment.” The account sheds light on the informal processes and the relational and agential dynamics at play in this laboratory of transnational environmental lawmaking, thereby illuminating and questioning the politics of policy-entrepreneurship and consensus-building—the tenuous and fragile modes of existence that mark contemporary international law.