Abstract: As the climate crisis intensifies, there is mounting pressure on international legal mechanisms to enforce state obligations in a meaningful manner. While the prevailing climate regime continues to be characterized by soft-law instruments, a novel dynamic is emerging within the domain of international investment law. Recent treaty practice and arbitral jurisprudence indicate that climate-related provisions in international investment agreements are undergoing a process of normative “hardening,” whereby soft commitments are interpreted as binding obligations. The present analysis posits that this transformation is being driven by a form of judicial activism, manifest through untraditional approach of treaty interpretation by investment tribunals or dispute panels, that expands the legal consequences of climate clauses beyond their original textual scope. Through a comparative textual analysis and case study examination, the article demonstrates how adjudicators are increasingly treating environmental and climate-related standards as norms of legal binding force. The present article provides a critical assessment of the implications of this trend, identifying two key risks: the alienation of IIL from its foundational goal of investment protection, and the erosion of state consent through the imposition of obligations not expressly agreed by states. By conceptualizing this trend as both a response to global regulatory failure and a potential source of institutional backlash, the article proposes a reframing of IIL as a hybrid governance regime. The analysis concludes that while judicial hardening may support climate enforcement, its long-term legitimacy will depend on preserving a delicate balance between environmental ambition, legal coherence, and sovereign consent.