This contribution argues that policymakers instrumentalise legal ambiguity to provide solutions to crises and achieve their preferences in complex governance systems. It looks at the Eurozone crisis and the introduction of sovereign debt restructuring as part of the policy solution. Despite initial opposition from the European Central Bank (ECB) and European Commission (EC), as well as negative market reactions, Greece’s debt was restructured in 2012. The notion of collective action clauses (CACs)—a private contractual term in bond documentation that enables bondholder coordination—was promoted as the credible tool for enabling sovereign debt restructuring. However, this paper argues that the success of CACs is related to how it functions as a boundary object, enabling a shared space of interpretive flexibility that allows policymakers to interpret CACs in terms of their preferences, despite a lack of consensus on the permissibility of future Eurozone sovereign debt restructurings. While enabling cooperation, this interpretive flexibility leads to different iterations of CACs—the Euro-CAC and Greece’s retrofit-CAC—which connects EU fiscal policy to monetary policy in a way that induces legal uncertainty as to the viability of future debt restructurings vis-à-vis the ECB’s bond-buying programmes.