In Pope Francis’ Encyclical on the environment, Laudato Si’, the leader of the Catholic church presents a moral argument for combating climate change and other environmental harm. As he has done throughout his papacy, the Pope highlights concerns about economic disparity, arguing that climate change disproportionally impacts developing nations and the world’s poor. Along with critiques of “consumerism” and the modern economic system, the Pope expressed deep skepticism about the motives and impacts of market mechanisms as emissions reduction tools. The Pope is not the first to challenge the ethics of market-based systems of environmental protection. Critics have argued that buying and selling pollution rights removes the moral stigma of pollution and that inequity is built into the system by allowing the rich to buy their way out of pollution reduction regimes. Others have worried that market systems can create pollution hotspots. But many others in the environmental community, particularly in the United States, have come to see market-based mechanisms as a potent, cost-effective, and morally and legally defensible way to achieve pollution reduction goals. On October 1, 2015, the Environmental Law Institute convened an expert panel to discuss the Pope’s position, its bearing on global efforts to curb greenhouse gas emissions, and how market-based methods of pollution control serve, or fail to serve, sustainability goals. This Dialogue presents a transcript of the discussion, which has been edited for style, clarity, and space considerations.