The lack of cooperation and prevalence of free riding in efforts to reduce emissions reflects the public good dilemma synonymous with climate change: whereby individual incentives lead to sub-optimal outcomes. This study examines how cooperative norms can be fostered through democratic processes. Specifically, we assess whether a given policy affects cooperation more significantly when it is democratically chosen by heterogeneous subjects as opposed to exogenously imposed by the experimenter. Subjects with differing marginal costs of abatement must democratically select an institution to reduce a national greenhouse gas inventory. By majority vote, subjects can choose between communication and two carbon tax variants. The experimental literature from studies with homogenous subjects suggests that cooperation improves when policy is endogenously selected as opposed to exogenously enforced. Overall we find that endogenous choice does not improve cooperation when subjects are heterogeneous. Furthermore, we find that, in the absence of a binding commitment, cooperation declines with endogenous choice as the prevalence of free-riding increases.