What are the origins and effects of legal ambiguity in authoritarian regimes? Much work on authoritarian legality identifies extensive ambiguity in how legal institutions operate——often simultaneously serving as sites of top-down authoritarian control as well as bottom-up societal resistance (Gallagher 2006, 2017; Moustafa 2007; El-Ghobashy 2008; Stern 2013; Chua 2012, 2014; Massoud 2013). In addition, underneath such operational ambiguity, many authoritarian systems also exhibit a great deal of ambiguity in the content of law itself: in what law says, what it allows, what it forbids, and sometimes——perhaps more fundamentally——whether particular rules or commands even count as “law” in the first place (Collier 1976; Stern 2010; Varol 2014; Druzin and Gordon 2018; Arslanalp and Erkmen 2020). Indeed, many features of authoritarian legal systems often appear vague and indeterminate, not just to those who study them but also to autocrats who rule over them, citizens who are ruled by them, judges who interpret and apply the law, and bureaucrats who operate the state’s legal machinery on a day-to-day basis. This paper develops a historical and institutionalist framework for understanding the dynamics of legal ambiguity under authoritarian rule. Leveraging a myriad of rich qualitative evidence, including 230 interviews with key Jordanian ministers, judges, lawyers, and activists, collected throughout more than three years of fieldwork in Jordan (January 2016–October 2019), we argue that path-dependent legal ambiguity can emerge——and plant deep institutional roots——through autocrats’ intentional, short-term efforts to address historical episodes of crisis. We do so through a fine-grained analysis of glaring ambiguities in how Jordan legally regulates one of the most basic questions of any political community: who is, and is not, a “citizen.” Our empirical inquiry begins by tracing the historical conditions that produced long-term and path-dependent legal ambiguity in policies governing the conditions under which one can lose Jordanian nationality. It then proceeds to probe the effects of legal ambiguity in Jordanian politics and courtrooms, which we find impacts how the state exercises its power just as much as it impacts how individuals experience the exercise of state power in their lives. Overall, this paper works to build a fruitful theory on how legal ambiguity emerges, as well as how it matters, in authoritarian environments using rich, difficult-to-access data from the Jordanian context.