This qualitative inquiry focuses on Canada's environmental assessment (EA) of the controversial-now defunct-Enbridge Northern Gateway Pipeline as a case study. Adapting Fairclough's (1992) approach to critical discourse analysis (CDA) as a methodological framework, I investigated how Northern Gateway's environmental effects were discursively framed and rationalized in relation to climate change, and how these discourses are connected to statutory interpretations and institutional norms. Using frame analysis and argumentation analysis as methods, I examined a corpus of publicly available Joint Review Panel (JRP) documents, federal statutes and official decision statements related to Northern Gateway's EA.Findings suggest that the convergence of particular discourses, ideologies, institutional power relations, and entrenched discretionary practices tended to marginalize and depoliticize climate change considerations in Northern Gateway's EA. These dynamics provided a foundation to rhetorically legitimate contentious project-related governance decisions, and arguably expose areas of potential concern in the contemporary EA and climate change context.