Laurianne Allezard

This chapter explores the French approach to legislative justification in the context of environmental and climate crises. While constitutional law in France recognizes an obligation to rationalize legislation, the enforcement of this duty remains weak and largely procedural. Scientific evidence—though increasingly central to democratic legitimacy—plays a limited role in constitutional review. Instead, legislative justifications often rely on vague or opportunistically invoked notions such as “general interest” or “urgency,” with minimal scrutiny from the Constitutional Council. Through an analysis of recent decisions and laws, the chapter shows how justification functions more as a rhetorical device than a binding legal constraint. It further highlights how scientific knowledge is instrumentalised selectively and frequently delegated to administrative or regulatory authorities with unclear accountability. In a time of polycrisis—where ecological, social, and institutional emergencies intersect and reinforce one another—the inadequacy of this framework raises concerns about the current and future legitimacy of law. The French case illustrates a classical constitutional posture, in which formalist habits and institutional inertia create obstacles to the development of more rational and sustainable responses to long-term crises. The chapter calls for an evolution beyond positivist formalism towards a constitutional culture grounded in empirical justification and transparent public reasoning.