This article addresses the bastardization of constitutional law in Argentina and the corrosive power of legacies of authoritarianism. It offers a genealogy of the use by Argentina’s Supreme Court of self-restraint canons from the time when they were borrowed from the US Supreme Court in the late nineteenth century. Partly resulting from the country’s experiences with military rule, the court transformed or expanded these canons, which entailed a gradual depreciation of statutes as the (uneasy) cornerstone of constitutionalism. Based on a fresh dataset and employing narrative and network analysis, the article focuses on a slogan the court has invoked since the 1960s: invalidating a rule is a matter of extreme institutional gravity and hence a strategy of last resort. Under the 1976–83 dictatorship, the court applied the slogan to various rules, including those passed by the military. It thus invoked familiar canons outside its scope conditions, conveying an illusion of constitutional regularity by masking the abnormal in acceptable garb and contributing to the regime’s legitimation. While the democratic court abandoned the most blatant expressions of authoritarianism, connections persisted, manifesting in the frequent citations to the dictatorship court’s use of the slogan and its extension to any rule. Authoritarian legacies die hard.