Despite some skepticism regarding its effectiveness, public participation has become a central facet of environmental decision making, including governments' various decisions to address climate change. However, the existing literature tends to address the general benefits of environmental public participation rather than examine details of how such participation actually occurs and how it differs among nations—even among nations all purportedly pursuing similar public participation goals. This article begins to fill that knowledge gap by examining law's key role in structuring how the public in different countries may actually participate in environmental decision making, including in unfolding national agendas to reduce greenhouse gas emissions and adapt to climate change impacts. Both the United States and European Union member states have decades of experience in writing—and rewriting—public participation into their environmental laws. This article actively explores and compares how the laws of the United States, the European Union, and the Netherlands (as an exemplar of an EU member state) structure public participation in environmental decision making in order to assess how far along the scale of public participation categories each government has progressed. It concludes that, for the moment, United States environmental law more often allows for public collaboration and empowers the public to make certain kinds of environmental decisions—although a new law in the Netherlands may soon encourage more creative and collaborative forms of public participation there, as well.