What factors explain variation in decisions to use force in American foreign policy? Consider the Obama administration’s decision to intervene in Libya. Upon assuming office, Obama outlined a foreign policy marked by a self-professed doctrine, ‘don’t do stupid shit’. In short, Obama sought to avoid the unnecessary use of military force, but when the threat of mass atrocity emerged, despite strong protests from senior advisers, he became drawn into the 2011 Libya intervention. By contrast, following chemical weapon attacks in Syria in 2013, Obama reneged on upholding his so-called ‘red-line’, pursuing diplomatic measures even though support for a military response was strong. But what explains this variation? Rationalist perspectives across the board have tended to overrate interpretive efficiency. Yet, such assumptions obscure the capacity for interests to be interpreted in different ways. To redress this issue, I build on discursive institutionalist insights, developing a model to show how principled and cognitive ideas act as weapons in institutional debates, serving to repress or displace information. To show how agents come to rely on principled or cognitive ideas, I develop a three-part model offering two mechanisms – cognitive repression and normative displacement – by which agents displace and repress certain types of information, depending on the ‘form’ in which that information is presented. This enables a more comprehensive understanding of how different interpretations lead to policy variation at critical moments of decision.