This chapter focuses on how different governance actors stress the constraining function of IIAs to achieve various goals and how they justify their actions. This chapter looks at how the IIA narratives have been used in reshaping national governance. This was chiefly through the narrative of IIAs as a disciplining and constraining force. We have identified that the general disciplining narrative about IIAs has three variants with different normative bents. These sub-types express how the governance actors evaluate the constraining potential of IIAs. On the one end of the spectrum, this disciplining effect may be viewed as flatly undesirable; on the other end, the constraint is viewed through a largely positive lens as a cultivating and educating force. Somewhat between sits the view of IIAs as simply something one must learn to live and deal with. Generally, the disciplining narratives about IIAs view IIAs as an incarnation of legal rationality superior to other rationalities, such as political or democratic rationality. Other considerations, even those pertaining to national constitutional arrangements, were cast in an inferior position and viewed as obstacles to a smooth implementation of IIAs.

This chapter argues that downplaying science in the judicial inquiry has a fundamental impact on the ways in which legitimate and persuasive reasoning can be crafted. More particularly, not respecting the cognitive authority of science undermines the epistemic legitimacy of decisions. The central yardstick in this respect is not that using more science would necessarily result in better-reasoned judgments; rather, the legitimacy of judgments hinges on how adjudicators reflect on the scientific aspects of disputes in the reasoning. The chapter identifies four types of epistemic yardsticks with which international fora justify the acceptance or rejection of a particular science-based claim. The chapter differentiates between legal, scientific, hybrid, and intuitive reasoning styles, and discusses the benefits and trade-offs of each of them in terms of factual accuracy, epistemic non-arbitrariness, practical feasibility, and preserving the judicial monopoly over adjudication. The chapter also offers solutions for remedying applicable shortcomings, and offers recommendations for selecting a sound approach to scientific knowledge in the judicial reasoning under particular circumstances.