This research shows how the participatory mechanism of popular consultation is helping local citizens in the environmental struggle involving La Colosa Mine in Colombia, against AngloGold Asahnti’s gold mining project. First, the legal and political context of the popular consultation is traced to the Colombian Constitution of 1991, which emerged as an answer to the bloody armed conflict in the country after a highly democratic and pluralistic process. Second, an assessment of the current research in procedural and substantive environmental justice in the U.S, Colombia and Latin America is done. Third, the following questions are answered through the analysis of the interviews held with the different actors in the case in the Cajamarca, Ibagué and Piedras municipalities and in Bogotá DC: Where did the idea of organizing a popular consultation come from? What were the effects, legal and social, in terms of environmental justice? Finally, a discussion of the findings is done. It is found that, in this case, the 1991 Constitution is the point of articulation of the environmental justice movement and the human rights discourse. This supports current research on how environmental justice and human rights movements are merging together as a global force for social change and democracy. Moreover, it is concluded that the popular consultation in La Colosa’s environmental struggle had ambiguous effects. On one hand, the popular consultation brought the Constitution to life and empowered people. On the other hand, the participatory mechanism was permeated by power imbalances created by extreme centralization in decision-making. The future remains uncertain for communities, environmental justice and peace in Colombia. However, as a concluding observation, it can be said that, whatever the popular consultation’s future may be, its existence created real opposition to the AngloGold Ashanti and gave energy to the environmental and human rights movements in Tolima and Colombia.