As environmental public participation has become increasingly mandated worldwide, its advantages and disadvantages have been widely documented. This article uses qualitative analysis of documentation and interviews with 40 participants in a US–Canadian International Joint Commission water management controversy. It demonstrates how ambiguity and diffuse power—that is, two characteristics of organizational pluralism—revealed in communication and governance contribute to the challenges of resolving the 13-year controversy. The article adds to the literature that has largely focused on power disparities between governing or managing organizations and stakeholders and makes recommendations for addressing situations involving organizational and scientific ambiguity as well as relatively equal distribution of power. Copyright © 2013 John Wiley & Sons, Ltd.