Frost C  omparative Migration Studies (2024) 12:23 or bylaw. Regulations are very flexible…No one can see them and criticize them, domestic or international.”3 Essentially, the use of implementing regulations to govern—virtually independent of corresponding domestic laws—represents a type of implementation gap between different levels of legislation, and this gap produces ambiguous policies that say different things in law versus regulations. Despite the prevalence of such ambiguous policies, particularly in citizenship and migration policies (Natter, 2021; Norman, 2020; Stel, 2020), few studies have focused on conceptualizing and operationalizing them, especially in contexts beyond North America and Europe. The relative absence of studies on law-regulation gaps contrasts with research on “discursive” policy gaps, which occur between a policy’s objectives and its laws (Castles, 2004; Hollifield et al., 2014), and “efficacy gaps,” which describe when a policy’s outcomes fail to meet its stated goals (Arcarazo & Freier, 2015; Czaika & de Haas, 2013). Other areas of study include “compliance gaps,” which reflect disparities between a state’s commitments to international law and its domestic policies (Akram, 2021; Búzás, 2016; Janmyr & Stevens, 2021; Stevens, 2013), and “protection gaps,” which occur when there are no legal rules to govern certain rights, particularly when those rights fall in between different legal frameworks (Akram, 2018; Akram et al., 2015; ElMufti, 2014; Chatelard, 2002). Another major area is “enforcement gaps,” when streetlevel bureaucrats do not properly apply laws on the ground (Holland, 2016; Ellermann, 2005; van Der Baaren, 2024), or when the institutional context surrounding the law’s enforcement (e.g., availability of information about the law or attitudes of bureaucrats) contrasts with the law’s content (Huddleston, 2020). Studies may devote less attention to law-regulation gaps because of assumptions that this gap, particularly in less-developed contexts, reflects institutional weakness and resource shortfalls that policymakers are unaware of or are incapable of resolving (Czaika & de Haas, 2013; Levitsky & Murillo, 2009). Another challenge in studying lawregulation gaps is that regulations, particularly in less-developed and more autocratic contexts, can be difficult to identify and track. In some cases, this can lead scholars to conclude that there is no policy, when instead, the policy is only taking place at the level of opaque regulations within particular ministries. Likewise, an emphasis on the “talk versus the walk of law” can overlook the role of subsidiary legislation, such as regulations, decisions, and instructions, in dictating the “walk” of law (Calavita, 2016, 109). Moreover, it can overlook differences within the “talk” of law when those differences materialize between primary (i.e., laws) and subsidiary legislation. Overall, there has been much research on legal gaps in citizenship and migration policy, both in and beyond Europe. However, few studies have focused on systematically examining gaps between a domestic law’s provisions and the implementation orders that guide the enforcement of those provisions. Exceptions, as discussed in the next section, include work that mentions potential examples of this gap, without characterizing it as a distinct type of legal gap or concept (e.g., Akram, 2018; Akram et al., 2015; Chatelard, 2002; Janmyr, 2016), studies that are beginning to conceptualize implementation gaps, with law-regulation gaps included as one category (van Der Baaren, 2024), and research 3 Jordanian former minister (TV54), October 2019. Page 2 of 18