Explaining variation in city sanctuary policies: insights from American and European cities

ABSTRACT This article draws on comparative evidence from four American and European cities – San Francisco, Houston, Barcelona, and Milan – to develop a framework for explaining variation in the types of sanctuary policies that city officials have adopted to protect and integrate undocumented immigrants into aspects of city life. While prior scholarship has focused on explaining whether cities adopt sanctuary policies at all, this article instead explains whether adopted policies bring symbolic or substantive benefits to undocumented immigrants and whether adopted policies conform to or confront the goals of national immigration policies. To explain the observed variation in adopted sanctuary policies across these four Global North cities, this article combines existing theoretical approaches to local immigration policymaking that emphasise the relevance of either city-specific contextual factors or the supra-local context in which different cities are embedded.


Introduction
With nativist politics on the rise in many Global North countries, undocumented (or unauthorised, irregular, illegalised, or out-of-status) immigrants have increasingly been denied basic rights and services while being subjected to aggressive policing, detention, and deportation (e.g. Crawley and Skleparis 2018). In contrast to anti-immigrant national policies and practices, a growing number of cities in the United States and Europe have become "sanctuary," "refuge," "solidarity," or "welcoming" cities that seek to protect and integrate these immigrants into city life (Darling and Bauder 2019;Huang and Liu 2018). 1 They have done so by developing policies and practices that include undocumented immigrants in public service provision, formal rights protections, and democratic participation modes (de Graauw 2021). While such inclusive local policies and practices are on the rise across Global North cities, there is little comparative research to elucidate the drivers behind them and the notable variation among them.
Scholars have analysed sanctuary-type city policies from distinct yet frequently disconnected theoretical perspectives. Notably, there is considerable research highlighting the relevance of city-specific contextual factors, including the characteristics of local immigrant populations; local political, partisan, and institutional dynamics; and the density and activism of community organisations (de Graauw and Vermeulen 2016;Huang and Liu 2018). Other scholars have instead focused on how supra-local factors such as national immigration policies have influenced city sanctuary policymaking. This approach, evidenced by the burgeoning scholarship on immigration federalism and multi-level governance, highlights that cities can pursue their own immigrant policies while navigating their hierarchical subordination to provincial, state, and national governments (Caponio and Jones-Correa 2018;Wells 2004). Not often, however, are these "localist" and "supra-localist" approaches brought together, which we believe is a missed opportunity to develop a fuller understanding of what drives variation in the extent and types of sanctuary policies different cities adopt.
This article offers a framework for explaining variation in city sanctuary policies. To do so, we combine insights from existing theoretical approaches in recognition of the fact that cities are uniquely situated at the crossroads of local and supra-local contexts that shape their responses to undocumented immigrants. Specifically, we argue that variation in local and supra-local contexts helps explain the types of sanctuary policies that cities may adopt. To map the diversity in city sanctuary policies, we propose a typology along two conceptual dimensions, i.e. policy content (ranging from symbolic to substantive protections for undocumented immigrants) and policy harmony (ranging from city sanctuary policies that conform to the goals of national immigration policies to those that instead confront or contravene them). These two dimensions are also reflected in several contributions in this special issue, which discuss degrees of effectiveness of sanctuary provided by territorial administrations and of contestation articulated through these policies. These range from merely symbolic declarations of sanctuary to building comprehensive firewalls around their jurisdictions (i.e. Humphris 2023; Mourão Permoser and Bauböck 2023; Wyn Edwards and Wisthaler 2023).
We draw on evidence from four American and European cities: San Francisco (USA), Houston (USA), Barcelona (Spain), and Milan (Italy). These cities represent a range of policies targeting undocumented immigrants, from symbolic policies that address their plight only rhetorically to substantive policies that offer them tangible benefits, and from conformist policies that echo the exclusionary goals of national or regional immigration regimes to confrontational policies that instead contravene them. All four cities have sizeable immigrant populations yet vary in their local economic, political, and civic contexts as well as the supra-local context in which city sanctuary policies are negotiated, developed, and implemented. For each city, we draw on assorted qualitative data to discuss how their policies vis-à-vis undocumented immigrants have evolved and characterise the policies in place.
Next, we first review key scholarly debates about city sanctuary policies in the United States and Europe before presenting our framework that brings these debates together in efforts to explain variation in the types of sanctuary policies adopted by different cities. We then discuss the article's methods and data, highlighting that San Francisco, Houston, Barcelona, and Milan are good initial cases for developing this framework. Our empirical examination of how government officials in these four cities have addressed issues facing undocumented immigrants underscores that cities' local and supra-local contexts need to be considered in tandem to explain what types of sanctuary policies they adopt. The article concludes by reflecting on the lessons learned from these four cities and outlining avenues for future research.

Making sense of city sanctuary policies
This article focuses on city sanctuary policies, an umbrella term we use to refer to different pro-immigrant city policiesincreasingly popular in the United States and Europethat address the needs and interests of undocumented immigrants, i.e. immigrants lacking legal status for one reason or another. To understand this growing local dimension of migration policymaking, scholars have pursued explanatory frameworks that depart from earlier studies focused on national citizenship regimes and models of incorporation (e.g. Brubaker 1998). We discuss two notable such approaches, which we call the "localist" and "supra-localist" approaches.

Localist approaches to understanding city sanctuary policies
Many scholars have emphasised the importance of city-specific demographic, political, and civic factors in explaining when city officials respond inclusively to issues affecting undocumented city residents. Collectively, they have highlighted that city officials governing cities with local contexts conducive to pro-undocumented policiesi.e. large immigrant populations, sufficient government resources, progressive political cultures, propitious institutional arrangements, and active community organisationsare more likely to enact sanctuary policies than those governing cities lacking these attributes.
Cities with large, concentrated, or rapidly growing foreign-born populations and cities that are fiscally sound are more likely to adopt sanctuary policies (Huang and Liu 2018;Walker and Leitner 2011). Partisanship is also important, and especially left-leaning city officials engage in sanctuary policymaking to galvanise their base and secure electoral rewards (Bazurli 2019;Ramakrishnan and Wong 2010), notably during times of national political polarisation on immigration issues (Collingwood and Gonzalez O'Brien 2019). City governmental institutions matter, too. For example, de Wilde and Nicholls (2021) find that American mayors operating in mayor-council systems, as opposed to council-manager ones, are better positioned to engage in sanctuary policymaking because they enjoy more administrative and budgetary authority as well as electoral incentives to heed migrants' interests. Finally, cities with denser and better developed infrastructures of immigrant and social movement organisations, labour unions, and faith-based institutions are more likely to adopt sanctuary policies (de Graauw and Vermeulen 2016;Mayer 2018;Steil and Vasi 2014). Such organisations provide city officials with important material, cognitive, and human resources for enacting and implementing sanctuary policies, while also playing crucial roles in representing undocumented immigrants in local claims-making arenas (de Graauw 2016).
While these localist approaches provide important insights into when city officials engage in sanctuary policymaking, they do not illuminate what types of sanctuary policies cities adopt. Also, they do not give much consideration to how the supra-local context in which cities are embeddedincluding those related to regional and national governmentsshapes city sanctuary policymaking.

Supra-localist approaches to understanding city sanctuary policies
Immigration and citizenship matters are typically the sole jurisdiction of nation states. Supra-localist approaches ask how cities in both the United States and Europe can navigate their subservient position in immigration policy to support undocumented immigrants facing exclusionary and punitive national immigration regimes. Among them are scholars of immigration federalism (Provine et al. 2016;Wells 2004) and multilevel governance (Caponio and Jones-Correa 2018;Scholten and Penninx 2016), who study how governmental and nongovernmental actors at different spatial scales shape local migration policymaking.
Considering cities' vertical and hierarchically-subordinate position vis-à-vis other government levels, scholars of supra-localist approaches have distinguished cities in federated compared with unitary government systems. Cities in the U.S. federal system, for example, can craft sanctuary policies in part because local governments have notable formal autonomy over healthcare, education, housing, and law enforcement issues, which directly impact the lives of undocumented and other immigrants (Varsanyi 2010). City officials in federal systems likely also have more opportunities to engage in sanctuary policymaking because authority dispersal across multiple government scales introduces policy ambiguities, contradictions, and loopholes that city officials can take advantage of through strategic venue shopping and issue framing (de Graauw 2021; Oomen et al. 2021;Wells 2004). Yet, government decentralisation can also pose barriers when state, regional, and other "middle-tier" governments increase their own engagement with immigration affairs and flex their hierarchical power over city officials, such as when U.S. states enact anti-immigrant laws that ban cities within that state from enacting sanctuary policies (Collingwood and Gonzalez O'Brien 2019).
City officials appear to enact sanctuary policies to counter forms of immigrant exclusion enshrined in national laws. Yet, different national immigration and citizenship regimes likely present city officials different opportunities and constraints to enact sanctuary policies. Restrictive immigration and citizenship regimes can constrain local opportunities to support undocumented immigrants yet also highlight the need for city sanctuary policies in the first place. Some scholarship in fact challenges the assumption that cities always pursue policies that are more inclusive of undocumented immigrants than national policies are. Delvino and Spencer (2014), for example, find that Italian laws provide some basic rights for undocumented immigrants, with municipalities subsequently enacting sanctuary policies conforming to these national provisions. Williamson (2020) similarly finds that local government officials in the United States tend to produce immigrant-focused policies that emulate the tenor and goals of federal policieswhether inclusive or exclusive of immigrantsthey are exposed to. All said, not all city sanctuary policymaking runs counter to national immigration policies and practices.
These supra-localist approaches also better explain whether or not city officials engage in sanctuary policymaking than they do variation in types of sanctuary policies different cities adopt. To better understand what sorts of policies city officials may develop to help undocumented immigrants, we believe it is important to combine localist and supra-localist approaches.

Explaining variation in city sanctuary policies
In combining localist and supra-localist approaches, we seek to explain variation in the types of sanctuary policies that different cities adopt. Not all city sanctuary policies are the same. In discussing sanctuary policies in New York City and San Francisco, de Graauw (2021) identifies policies aimed at including undocumented immigrants in local public service provision (e.g. healthcare, housing, and legal services), formal rights protections (e.g. protection from deportation and labour rights protections), and democratic participation modes (e.g. local voting rights and the ability to serve on local government commissions). In analysing pro-undocumented policies in Swiss cities, Kaufmann and Strebel (2021) distinguish between sanctuary city, local bureaucratic membership, and regularisation policies. In this special issue, Bauböck and Mourão Permoser (2023) propose a similar but more general distinction between sanctuary, firewalls, and regularisation as three inclusive responses to the presence of undocumented immigrants. Though not offering a policy typology, Bauder and Gonzalez (2018) uncover different legal, discursive, identity-formative, and scalar aspects of city sanctuary policies, also suggesting these might differ depending on the specific national context in which they are implemented. In all, there are different ways to typologise city sanctuary policies.
Building on these efforts, we propose a typology of city sanctuary policies along two conceptual dimensions: policy content and policy harmony. Policy content captures a continuum of symbolic to substantive protections for undocumented immigrants, whereas policy harmony captures a continuum of policies conforming to the goals of national immigration policies to those confronting them. This creates four possible ideal types of city sanctuary policies: (a) symbolic-conformist, including welcoming city declarations that celebrate immigrant diversity and other rhetorical initiatives that do not challenge immigrant exclusions enshrined in national laws; (b) symbolic-confrontational, including city laws that explicitly recognise undocumented residents as integral parts of the city community and blame national authorities for their plight, as well as that ban the local use of the terms "illegal immigrant" and "illegal alien" commonly used in national laws; (c) substantive-conformist, such as city policies that extend healthcare and education services to undocumented immigrants based on existing constitutional norms, human rights laws, or court decisions to which all government levels must adhere, as well as local wage policies that emulate labour rights protections already offered by national policies; and (d) substantive-confrontational, such as city policies that make healthcare and education services available to undocumented immigrants in contravention of national restrictions, as well as "don't ask, don't tell policies" that put an effective firewall between local police and national immigration authorities.
This basic framework presents ideal-typical policies, though in real life the boundaries between conceptual categories are likely fuzzy and sometimes overlapping. With regard to policy content, symbolic sanctuary declarations may in fact produce substantive outcomes, such as immigrants' strong feelings of community belonging and a sense of efficacy among activists (Bauder and Gonzalez 2018), thus possibly building capacity for more substantive sanctuary policies down the road. Policy harmony, too, can escape clear-cut categorisations as city sanctuary policies can be simultaneously disruptive and conforming (de Graauw 2021). Additionally, sanctuary policies are not always static and can change over time. Confrontational policies can be challenged in court and judicially weakened to conformist policies. Alternatively, newly enacted pro-immigrant policies at the state and national levels can incentivise cities to strengthen their symbolic-conformist sanctuary policies to policies more substantive or confrontational in nature. These caveats notwithstanding, the proposed four ideal-types can serve as heuristic devices to compare city sanctuary policies and explain variation among them.
We argue that both localist and supra-localist contextual factors influence the type of sanctuary policies cities may adopt. City officials likely adopt sanctuary policies that are symbolic-conformist when neither the local nor the supra-local context is conducive to sanctuary city policymaking, such as when city officials confront conservative voters, limited resources, and anti-immigrant civil society organisations while also struggling with limited autonomy to confront restrictive national immigration policies. Symbolicconformist city sanctuary policies are also likely when local contextual factors prevent city officials from taking advantage of institutional openings that the supra-local context may provide for more substantive or confrontational policies. Symbolic-confrontational city sanctuary policies are likely adopted when opposition to restrictive national immigration policies is popular among local voters and civil society organisations, especially in times of national political polarisation on immigration issues, but city officials operate in a supra-local context offering them little to no autonomy. Substantive-conformist sanctuary policies are likely adopted when local contexts are conducive to addressing the plight of undocumented immigrants, but city officials want to avoid intergovernmental conflict and opt to extend to undocumented immigrants only the few rights and benefits already provided in national legislation. Finally, city officials likely adopt sanctuary policies of a substantive-confrontational nature when they operate in a favourable local context as well as a favourable supra-local context that provides openings for crafting oppositional local policies.

Methods and data
We compare sanctuary policymaking in San Francisco (USA), Houston (USA), Barcelona (Spain), and Milan (Italy), cities with sizeable immigrant and undocumented populations yet variation in their local economic, political, and civic context as well as the supra-local context in which they are embedded (see Table 1). They represent a range of sanctuary policy interventions that can also be encountered in other Global North cities, which makes them useful cases to explore how local and supra-local contexts may drive variation in the types of sanctuary policies different cities adopt. This case selection is informed by our in-depth knowledge of these four cities developed for other projects, allowing us to assess similarities and differences across and between them, thereby engaging in inductive theory-building. Additional research on sanctuary policymaking in other cities will be necessary to systematically test, and possibly refine and extend, the framework developed out of the experiences of these four cities.

Research sites
City officials in San Francisco (California) and Houston (Texas) operate in the same national context but different state and city contexts. The United States, a classic immigration country, has no formal integration programme and today takes a hard line on immigration enforcement. California is pro-immigrant and the Democrat-controlled state government has enacted many state laws protecting undocumented immigrants, while Texas is anti-immigrant and the Republican-controlled state government has restricted the rights of immigrants and refugees in recent years (Pham and Van 2016). The United States has a federal system, with powers divided and shared between the federal, state, and local governments. Cities enjoy notable state-delegated powers to protect and promote the health, safety, and welfare of all city residents. Additionally, the multi-layered structure of the U.S. federal system has produced ambiguities and contradictionsbetween different federal government branches and between different government levelsin the treatment of undocumented immigrants (Provine et al. 2016;Wells 2004). This provides openings for city officials to engage in sanctuary policymaking, but their city context likely shapes how and to what extent they do so.
San Francisco provides an opportune city context for enacting sanctuary policies that are substantive and confrontational in nature. It is the 14th largest U.S. city and home to about 875,000 residents, 34 percent of whom are foreign-born, including an estimated 49,000 undocumented immigrants (MPI 2016a). City officials have the fiscal resources to make sanctuary policies a reality, given that the Bay Area's booming tech economy has boosted the city's tax revenues (Storper et al. 2015). San Francisco's political culture is progressive: the vast majority of San Franciscans have supported Democratic candidates in recent presidential elections, and the majority of city legislators self-identify as progressives (Siegel 2019). Finally, San Francisco has a thick and robust organisational landscape, and immigrant organisations are numerous and very active in local politics (de Graauw 2016). Houston offers a less opportune local context, likely resulting in sanctuary policies that are more symbolic and conformist in nature. Houston is the fourth largest U.S. city, with about 2.3 million residents. Twenty-nine percent of Houstonians are foreign-born, including an estimated 412,000 undocumented immigrants (MPI 2016b). City officials lack the fiscal resources to make sanctuary policies a reality: despite a booming economy, the city has struggled with budget deficits due to caps on its taxing power and skyrocketing costs of the city's municipal pension system (Fulton et al. 2020). Houston has long been politically divided, with the balance of power oscillating between Democrats and Republicans, though Democrats have gained ground in recent elections. Houston has a less developed and sparser infrastructure of civil society organisations with relatively few (though a growing number of) immigrant organisations (Gleeson 2012).
With over 1.6 million residents, Barcelona is the second largest city in Spain, a European border country relatively new to mass immigration. Spain has a quasi-federal system, where the central government has exclusive power over immigration, and 17 autonomous communities enjoy strong regional autonomy. Navigating EU enforcement pressures and Spaniards' relatively open attitudes toward immigration, Spain offers a mixed enforcement-integration national context. While taking a hard line on asylum seekers, it also offers some stable regularisation pathways and grants the autonomous communities power over integration issues (Garcés-Mascareñas 2014). Spanish municipalities also have some leeway in how they choose to deal with undocumented immigrants due to their responsibility to register all new city residents (empadronamiento), which is critical for immigrants' access to public services and regularisation procedures.
Overall, Barcelona provides a favourable local context for sanctuary policies that are substantive and confrontational in nature. About a third (29%) of its residents are foreign-born, including an estimated 30,000 undocumented immigrants. 2 Its transition to a service economy has made it a relatively affluent city. Long a progressive haven, Barcelona has been governed since 2015 by Barcelona en Comú (Barcelona in Common), a radical-left citizen platform committed to promoting social justice, community rights, and participatory democracy (Blanco, Salazar, and Bianchi 2020). Barcelona is located in the notably pro-immigrant Catalonia regional government and has a robust infrastructure of civil society organisations that have long fought for housing and immigrant rights (Garcés-Mascareñas 2014).
Finally, with nearly 1.4 million residents, Milan is the second largest city in Italy, a European border country with a unitary but decentralised government and a relative newcomer to mass immigration. The central government has sole immigration power, with policies increasingly focused on enforcement amid growing popularity of farright national politics (Bazurli and Campomori 2022;Tuckett 2018). Undocumented immigrants enjoy few regularisation opportunities and deportation protections, and they cannot access public services other than basic healthcare and education (Delvino and Spencer 2014). Italian regional governments enjoy some autonomy in welfare service provision, and some progressive regions have adopted pro-undocumented policies (Piccoli 2020). Unable to register undocumented residents and having little sway over local policing practices, municipalities in contrast have limited powers to enact city sanctuary policies.
Overall, Milan has a less opportune local context, likely resulting in mostly symbolic and conformist policies. A fifth (20%) of its population is non-Italian, including an estimated 47,000 undocumented immigrants (ORIM 2020). It is a relatively affluent post-industrial city with significant funding earmarked for local welfare programmes. Since 2011, centreleft political coalitions, headed by the Partito Democratico (Democratic Party), have ruled city government. However, Milan's political culture historically has been divided, also on immigration issues, and city politics must contend with strong anti-immigrant parties in the Lombardy region. Milan has an extensive network of community activists, though immigrant organisations lack prominence (Campomori and Caponio 2017).

Data
This article draws on two qualitative studies addressing immigrant rights in San Francisco and Houston between 2005 and 2018 (e.g. de Graauw 2016; de Graauw and Gleeson 2021) and a third qualitative study on immigrant rights in Barcelona and Milan between 2017 and 2019 (e.g. Bazurli 2019). These three projects, while developed separately, all focus on how city government officials and civil society actors have interacted with each otherin collaborative and confrontational waysto address the rights of immigrants, including undocumented ones. Together, they provide a rich empirical basis for examining how local and supra-local contexts have shaped the types of sanctuary city policies adopted across these four cities.
This article gleans insights from 107 interviews with two sets of respondents: local elected and appointed city officials (20 in San Francisco, 11 in Houston, 7 in Barcelona, 6 in Milan) and staff from local immigrant and other community organisations (17 in San Francisco,15 in Houston,18 in Barcelona,13 in Milan). These respondents were selected to represent a range of perspectives on the local politics of immigrant rights in these cities. Interviews lasted one to two hours, with questions focused on how, why, and to what ends city officials and community advocates sought to advance the rights of immigrants, including undocumented immigrants, and the challenges they met along the way. Interviews were audio recorded, fully transcribed, and re-analysed for this articlewith multiple rounds of coding reflecting between-author conversations to examine how local and supra-local contexts influence the types of sanctuary policies enacted by city officials. We complement our interview data with analysis of local newspaper reports, government files, and secondary literature on sanctuary policymaking in the four cities under study.

San Francisco sanctuary policies: substantive and confrontational
San Francisco has been a sanctuary city since 1985, when city legislatorswith pressure from local activistsadopted a resolution and, four years later, an ordinance prohibiting city employeesin all but limited circumstancesfrom using municipal resources to enforce federal immigration laws, asking about immigration status, or communicating information about suspected undocumented immigrants for federal immigration enforcement purposes. Originally, San Francisco's sanctuary policy focused on helping 60,000-100,000 federally non-recognised refugees from Central America unable to gain political asylum in the United States (Guevarra and Farrell 1985). Over time, however, as one city administrative official discussed, it inspired the development of "additional policies aimed at protecting all undocumented immigrants." 3 In all, San Francisco's sanctuary policies today are substantive and confrontational in nature: they bring tangible benefits to undocumented immigrants and contravene the federal government's twin goals of immigration enforcement and restriction of undocumented immigrants' rights.
San Francisco's 1989 sanctuary ordinance, called the City of Refuge Ordinance, constituted the city's "first real effort to protect and to make available basic city services to undocumented immigrants," the same city official explained. 4 Since then, city officials have developed additional policies aimed at improving undocumented immigrants' access to city services. Notable are policies from 2001 and 2007, respectively, creating language access requirements for city agencies and municipal ID cards for all San Francisco residentsregardless of citizenship and documentation statusthat, as several government and civil society respondents explained, have made it easier and safer for undocumented immigrants to interact with frontline city workers. 5 Also, while federal welfare reform legislation from 1996 made undocumented immigrants ineligible for most publicly-funded health services, San Francisco officials launched the Healthy San Francisco programme in 2007 to provide comprehensive health services to 73,000 uninsured city residents, again regardless of citizenship and documentation status (Katz 2008). And in response to the federal government's expanding campaign during the Trump administration to expel all undocumented immigrants from the country, San Francisco officials started funding the city's Public Defender's Immigration Unit in 2017 to offer legal services to residents facing deportation (Green 2017).
San Francisco officials have also expanded upon the original firewall protections by enacting additional rights protections for undocumented immigrants. Since 2000, they have strengthened the local workplace rights of undocumented workers by enacting living wage, minimum wage, and anti-wage theft ordinances. "In San Francisco," one labour organiser reflected, "we've passed more inaugural and progressive pieces of labour rights legislation than anywhere else," adding that this was made possible because of sustained advocacy by a vibrant coalition of labour and immigrant rights organisations. 6 As a result, in early 2023, the San Francisco hourly minimum wage for all workers stood at $16.99, compared to $15.50 at the state level and $7.25 at the federal level. Sanctuary has also been expanded through the adoption of voter initiatives that provide new democratic participation modes for some undocumented immigrants. San Francisco is among the handful of U.S. cities offering local voting rights to noncitizens, which according to one immigrant rights leader "marked a historic win culminating 15 years of advocacy … finally giving immigrants a say at the ballot box." 7 Specifically, since 2016, the undocumented parents of students in the San Francisco Unified School District can vote in local school board elections. Since 2013, some city legislators have engaged in participatory budgeting, enabling undocumented immigrants to discuss, prioritise, and vote with other residents on how to allocate part of the city budget for that legislator's district (de Graauw 2021). Finally, since 2020, undocumented immigrants can be appointed to city boards and commissions, which play important advisory roles in city politics (Hom 2020).
The adoption of many substantive and confrontational sanctuary policies is partly explained by the supra-local context. San Francisco officials have managed to include undocumented immigrants in basic service provision by capitalising on their state-delegated powers to develop services that protect and promote the health, safety, and welfare of all city residents (de Graauw 2021). In fact, as one elected city official's staffer reflected, many city sanctuary policies have been "framed broadly as non-controversial, non-immigrant issues … making the city better for everyone." 8 Additionally, they have managed to include undocumented immigrants in rights protections and democratic participation modes by taking advantage of the multi-layered and internally contradictory structure of the U.S. federal system, which has created loopholes and thus openings for local policies that diverge from federal ones (Wells 2004). With local workplace rights, San Francisco policymakers capitalised on the divergent goals of federal immigration and labour laws. Immigration laws are exclusive and seek to identify, apprehend, and expel undocumented immigrants, while labour laws are inclusive and seek to protect the workplace rights of all workers (Gleeson 2012). Towards developing local workplace policies inclusive of undocumented immigrants, one labour leader explained, community pressure "moved city officials to focus" their policymaking on the immigrant-inclusive domain of labour laws. 9 Similarly, with extending local voting rights to some undocumented immigrants, San Francisco policymakers took advantage of a loophole in 1996 federal legislation making it illegal for noncitizens to vote in federal, though not state and local, elections (Hayduk 2006).
While the supra-local context created opportunities for substantive and confrontational sanctuary policies, local contextual factors enabled San Francisco city officials to realise them. In San Francisco, community organisations have long advocated for undocumented immigrants, putting constant pressure on city officials to act (de Graauw 2016). Since the early 2000s, when the city switched from an at-large to district electoral system, San Francisco has had a growing number of progressive city government activists, or local legislators who are proactive, strategic, and creative in using their policymaking powers to address the needs of undocumented residents (de Graauw 2021). And while local voters have not always supported undocumented immigrants, as one immigrant rights advocate reflected, "at critical moments, they've voted based on local progressive values," such as when they approved ballot measures that extend to them voting rights in local school board elections and allow them to be appointed to city boards and commissions. 10 Finally, San Francisco officials have had the financial resources needed to enact and implement substantive and confrontational sanctuary policies, some of which "have steep price tags," as one city administrative official mentioned. 11

Houston sanctuary policies: symbolic and conformist
Houston city officials never enacted a sanctuary ordinance to create a firewall between local police and federal immigration authorities and make basic city services available to undocumented immigrants. In 2016, however, Mayor Sylvester Turner proclaimed Houston to be a "Welcoming City" and, with philanthropic support, formed a multisector task force responsible for recommending city policies to promote immigrant integration (Welcoming Houston 2017). Task force recommendations include several interventions that amount to substantive and confrontational sanctuary policies, but these have not yet been realised. While Houston city officials have improved language accessibility in city service provision and enacted legislation to stop wage theft, overall Houston's few sanctuary policies are symbolic and conformist in nature: they bring few tangible benefits to undocumented immigrants and do not confront the goals of national enforcement policies.
In Houston, according to one immigrant rights advocate, police-immigrant relations "have long been controversial." 12 Because city legislators include both Republicans and Democrats, there is no majority support for creating an immigration enforcement firewall. Instead, community advocates have focused on keeping city police out of the federal 287(g) programme, which incentivises local law enforcement cooperation with federal immigration authorities. And while the Houston Police Department does not permit its officers to apprehend and detain undocumented immigrants simply because of their unauthorised status, this has been "largely an empty victory," the same advocate explained. 13 Notably, the Sheriff's Office of Harris Countya larger and more conservative political jurisdiction that encompasses most of the city of Houstonhad a 287(g) agreement in place between 2008 and 2017, which served as a deportation dragnet and earned Houston the label of "deportation capital" of the United States (Duong 2016). And while years of community pressure finally moved Harris County to end its 287(g) agreement in 2017, it continues to be among the counties with the highest number of federal immigration arrests (TRAC 2018). In all, Houston is still not a safe place for undocumented immigrants.
Houston city officials have supported public services for undocumented immigrants only selectively and inconsistently, with no large public outlays. At different points in recent history, for example, they created and subsequently defunded three centres offering employment and English language services to undocumented day labourers (Gleeson 2012). In 2013, Mayor Annise Parker signed an executive order requiring city departments to offer services in the top five commonly-used foreign languages in Houston, befitting "an international city of commerce, culture, trade, travel, and tourism." 14 Finally, while city officials collaborate with community organisations to help legal immigrants to become U.S. citizens, they neither fund nor offer legal services to undocumented immigrants. In 2013, this task was instead assumed by the Houston Endowment and the Simmons Foundation, two local foundations thataccording to one foundation officialformed "a nonprofit collaborative to increase legal services capacity" and to streamline the ability of low-income immigrants to access holistic immigration legal services, including assistance in fighting deportation and securing asylum status. 15 City officials have rarely initiated or enacted new rights protections for undocumented Houstonians. However, in 2013, "after months of tireless advocacy" by immigrant and labour advocates, they enacted the Anti-Wage Theft Ordinance. 16 Limited in reach, this ordinance aims to deter employers from stealing workers' wages by banning those who do from being able to renew assorted city licenses necessary to operate in Houston (Morris 2013). Earlier, in 1997, voters overwhelmingly rejected (by 77%) a ballot initiative to raise Houston's hourly minimum wage from $4.75 to $6.50, which would have been a boon to low-wage undocumented workers (Langford 1997). Finally, Houston does not offer undocumented immigrants local voting rights, does not allow them to serve on city boards and commissions, and does not have a participatory budgeting process.
Overall, Houston city officials have not engaged in much sanctuary city policymaking even though the city has a very large undocumented population, and the few sanctuary-type policies and programmes they have adopted are mostly symbolic and conformist in nature. Local law enforcement has done little to prevent federal immigration authorities from identifying, apprehending, and expelling undocumented city residents. Houston's "Welcoming City" status is, thus far, largely a rhetorical initiative. The mayor's language access executive order, as one city administrative official explained, was developed "[following] guidance from Title VI of the federal Civil Rights Act of 1964," which bans discrimination on the basis of race, colour, or national origin in any programme or activity receiving federal financial assistance. 17 And Houston's Anti-Wage Theft Ordinance merely seeks to prevent local employers from stealing the minimally required wages that all workers are entitled to by federal labour law.
The U.S. federal system provides Houston officials with openings to develop substantive and confrontational sanctuary policies, but that they have not followed in San Francisco's footsteps can be explained by local and state contextual factors. Over the years, there have been several notable immigrant rights supporters on Houston's city council (e.g. former Councilmembers Mike Laster and Ed Gonzalez), but several respondents noted that the countervailing pressures of small government ethos, ongoing budget shortfalls, large numbers of conservative voters, and a vocal contingent of anti-immigrant forces (including former Councilmembers Orlando Sanchez and Helena Brown) have prevented Houston government from embracing the city's undocumented immigrants more fully. 18 Immigrant and other community organisations, which are fewer and less developed than in San Francisco, have wielded only limited power in this space. And if Houston city officials take cues from state officials, Texas' anti-immigrant policy contextnotably with passage of SB4, a 2017 state law effectively preempting Texas cities from instituting immigration enforcement firewallsdoes not encourage them to enact sanctuary policies more substantive or confrontational in nature.

Barcelona sanctuary policies: substantive and confrontational
Barcelona has a long history of pro-immigrant local policies, first developed in the late 1990s when there were few foreign-born residents in the city. Two key principles have guided these early and subsequent sanctuary policies: equal rights and opportunities for all city residents, and diversity. In discussing Barcelona's long-term commitment to the rights of all immigrants, one high-level city administrator commented that "the hard core of policies, their main concepts, have always remained the same." 19 These same inclusive principles have also informed the policymaking of the Catalan regional government, which launched its first integration and diversity programmes also during the 1990swell in advance of Spanish central authorities. In all, Barcelona's sanctuary policies today are both substantive and confrontational: they bring tangible benefits to undocumented immigrants and confront the Spanish government's and the EU's goal of immigration control and enforcement.
While sanctuary policies date from the 1990s, in 2017 Barcelona city officials developed a comprehensive and substantive sanctuary action plan to include undocumented immigrants in public service provision and new rights protections (Ajuntament de Barcelona 2017). The same administrator explained that the condition of undocumented immigrants had become "the utmost priority" of the Barcelona en Comú administration, adding that the plan framed "irregularity in positive terms" and that "this is extremely innovative" also because city officials openly talked about it. 20 The plan seeks to make full citizens out of city residents who are illegalised by EU and Spanish immigration laws by offering language courses and legal services and by encouraging also undocumented immigrants to register with the city so that they, too, have access to municipal services. Barcelona's sanctuary action plan, moreover, promotes status regularisation, thereby protecting undocumented immigrants from detention and deportation. Specifically, Spanish municipalities are tasked with preparing "integration reports" for undocumented immigrants who want to regularise their status with the Spanish national government, which they can do after three years of residence and/or work in the country (Garcés-Mascareñas 2014). Barcelona city officials have promoted and facilitated status regularisation by using immigrants' city registration as proof of integration. Also, they have developed employment plans (plans d'ocupació) to hire undocumented immigrants in year-long positions in government or nonprofit cooperatives, also with the goal of demonstrating integration and facilitating regularisation.
Barcelona city officials have also included undocumented immigrants in democratic participation modes, notably through the Consell Municipal d'Immigració (Municipal Immigration Council). The Consell, an advisory and participatory body of the Barcelona City Council established in 1997, enables immigrant-led organisations to be involved in local migration governance. Long accused of tokenism, being dominated by well-established nongovernmental organisations, and operating in a top-down manner (Però 2007), the Consell's powers and legitimacy have been revamped under the Barcelona en Comú administration. The new administration paved the way for greater influence for "new, more radical organisations," one labour leader serving on the Consell explained, to the detriment of "the 'old caste'" of community organisations. 21 "To date," one elected city official commented, "we have enacted 100% of the [Consell's] proposals that are within the municipality's power to enact." 22 In fact, the Consell had a hand in promoting and developing the 2017 sanctuary action plan discussed earlier.
The supra-local context in which Barcelona city officials operate partly explains their adoption of substantive and confrontational sanctuary policies. Notably, they have capitalised on administrative tasks delegated to them by the national government to pursue their own political goalsin the words of one elected city official, "we stretched [national laws] like chewing gum." 23 Specifically, they have taken advantage of their resident registration powers to register undocumented immigrants, include them in municipal service provision, and provide proof of their integration to facilitate status regularisation. By relying on municipalities for key administrative functions such as resident registration, Spain's central government has provided city officials with opportunities to counter restrictive national immigration policies and expand access to integrative measures such as Spain's regularisation programme dating from 2004. Additionally, the Catalan regional government is notably pro-immigrant, extending comprehensive healthcare services to undocumented immigrants, thus sending pro-immigrant signals to Barcelona policymakers. 24 There are limits, however, to Barcelona's sanctuary powers: Spain's law enforcement is highly centralised, and Barcelona city officials cannot prevent central authorities from identifying, apprehending, and expelling undocumented immigrants ineligible for regularisation (Bazurli and Delclós 2021).
The supra-local context created opportunities for substantive and confrontational sanctuary policies, but local contextual factors enabled city officials to realise them. Barcelona's political context has long been inclusive of undocumented immigrants, but the 2015 breakthrough of Barcelona en Comú, a unique progressive movement-party coalition, allowed many immigrant rights activists to become key decisionmakers in local politics (Blanco, Salazar, and Bianchi 2020). In Barcelona, "the boundaries between the state and society have become extremely blurred," one elected city official commented, adding that "high-ranked officials are still deeply embedded within activist networks." 25 Local voters tend to have progressive views on immigration so that local political parties risk electoral retribution if they do not frame immigration issues inclusively (Bazurli 2019). The city also has had the resources to devote to sanctuary policies, allocating about €580,000 in 2017-18 alone to the implementation of the 2017 sanctuary action plan (Ajuntament de Barcelona 2017). Finally, the city has a tradition of community-based activism, with community organisations having notable political clout, including over local immigration issues (Bazurli 2019).

Milan sanctuary policies: symbolic and conformist
Between 1993 and 2011, conservative and far-right political parties governed Milan, making the city a laboratory for nativist politics (Delvino and Spencer 2014). Besides restrictions on welfare programmes, city officials then also touted crackdowns on immigrants and other minoritised populations, whom they viewed as economic, cultural, and security threats. Key targets were undocumented immigrants, who faced local police raids on public transportation and whose children were excluded from public kindergarten schools (e.g. Rossi 2007). In Milan at the time, being a foreigner meant "living with the police who could ask you for your residence permit at any time," one immigrant activist commented, adding that "if you were caught on the tram without a ticket, you're in real trouble; if you had no residence permit, you could easily end up in immigrant detention." 26 Left-leaning political parties, on the promise of developing more pro-immigrant city policies, took over city government in 2011 after a heated electoral campaign that involved many community organisations. Since then, Milan city officials have dismantled many of the earlier exclusionary policies and rebranded Milan a "Welcoming City" (Bazurli 2019). Yet the sanctuary policies adopted since then are largely symbolic and conformist in nature: they have brought few tangible benefits to undocumented immigrants without really confronting the restrictionist goals of national immigration policies.
Milan's city government has offered public services to undocumented immigrants only selectively and sporadically. While children of undocumented city residents were readmitted to public kindergartens soon after the 2011 local elections, Milan city officials have not created new sanctuary benefits for undocumented immigrants (Bazurli 2019). For example, while welfare plans adopted by the new administration marked a sea change in the city's approach to immigrant integration, they did not include undocumented immigrants (Comune di Milano 2012). Also, in 2017, city officials made it easier for marginalised city residentsespecially those without a fixed home addressto register as city residents, a service not extended to undocumented immigrants either, despite grassroots demands for their inclusion (Dazzi 2019). 27 The activist network Nessuno è Illegale (No One Is Illegal) indeed demanded "the immediate […] registration of, and extension of rights to, the entire citizenship, meaning whoever resides in Milan, without discrimination based on nationality." 28 Civil society organisations now fill important gaps in municipal services, offering critical healthcare, housing, and legal counselling to Milan's undocumented immigrants (Ambrosini 2015).
City officials have also done little to develop or implement new rights protections or democratic participation modes for undocumented immigrants. While city officials installed after the 2011 municipal elections ended the raids by local police on public transportation and managed to close the Via Corelli detention centre in the eastern part of Milan from 2014 to 2018 29 , deportations in Milan have continued and even increased since 2017, amid rising right-wing nativism nationally. Also, national law enforcement officials stationed in Milan have increasingly restricted immigrant rights by aggressively policing people of colour in public spaces and by creating arbitrary administrative practices at their Milan offices that make it harder for immigrants to access critical documents needed to legalise their status (Artero and Fontanari 2021). Finally, undocumented immigrants remain largely excluded from local governance. While the post-2011 left-leaning city officials have developed new participatory structuresnotably the Forum Terzo Settore (Third Sector Forum)to include community organisations in local decision-making, immigrant-led organisations have continued to be fragmented, poorly resourced, and crowded out by native-led organisations purporting to represent immigrants' interests. 30 Italy's supra-local context helps explain Milan's adoption of mostly symbolic and conformist sanctuary policies. Italy's government system constrains municipalities, leaving Milan city officials almost no opportunities to develop local policies that deviate from national ones. 31 Unlike Barcelona city officials, Milan city officials cannot include undocumented immigrants in the city registry, which is also a gateway to government services in Italy. This is "something that the city government can't do," one activist leading the registration campaign reflected, adding that nonetheless it "is an important question of principle for us." 32 The decision to readmit the children of undocumented immigrants to public kindergartens in 2011 simply followed national law and court jurisprudence, which entitle all childrenincluding those with undocumented parentsto a public education and made unlawful city policies to the contrary (Delvino and Spencer 2014). Finally, Milan city officials could not create an immigration enforcement firewall. While they had the power to prevent some aggressive practices by local police, they could not prevent national police officials from enforcing in Milan the increasingly restrictive national immigration laws. There are "national rules that public administrations must necessarily comply with," one city administrator matter-of-factly reflected. 33 Finally, the Lombardy region has long pursued an anti-immigrant agenda, thus not cuing Milan city officials to pursue more substantive or confrontational city sanctuary policies.
Local context further explains why Milan's sanctuary policies have been mostly symbolic and conformist. Left-leaning politicians came to power only in 2011 after bitterfought municipal elections, leading a city that had long practiced anti-immigrant politics. Pro-immigrant organisations, one respondent explained, "were awaiting the election of [a left-leaning city government] like the desert awaits water." 34 This meant that sanctuary policies had to be developed from scratch, with initial policy energies focused on dismantling the exclusionary policies from prior administrations. The persistent opposition of a vocal contingent of anti-immigrant forces in city government (including former Councilmember Matteo Salvini, current leader of the far-right Lega political party) has also prevented Milan city government from embracing undocumented immigrants more fully. This divided political landscape has also made it challenging for pro-immigrant community organisations to build sustained collaborations with city officials (Bazurli 2019).

Conclusion
This article has offered a framework for explaining variation in sanctuary policies across immigrant-dense Global North cities. The type of sanctuary policies city officials adopti.e. symbolic or substantive, conformist or confrontationalcan be explained by considering both city-specific contextual factors and the supra-local context in which cities are embedded. We draw on comparative insights from San Francisco, Houston, Barcelona, and Milan, but our findings likely extend beyond these four cities.
The supra-local context sets important parameters for city sanctuary policymaking. In the U.S. federal system, city officials can develop sanctuary policies that are both substantive and confrontational in nature. San Francisco city officials have developed numerous policies that bring tangible benefits to undocumented immigrants and confront federal enforcement policies by taking advantage of their autonomy in a range of policy domains and the policy ambiguities, contradictions, and loopholes that authority dispersal across multiple government scales has introduced. In Spain's quasi-federal system, Barcelona city officials have similarly benefitted from state-delegated administrative functions, notably cities' responsibility to register all city residents and assist in status regularisation procedures, to enact substantive and confrontational sanctuary policies. In contrast, Milan city officials have been constrained by lack of local autonomy in Italy's more centralised system, limiting them to adopt sanctuary policies that are mostly symbolic and conformist in nature.
Local contextual factors further influence how city officials engage in sanctuary policymaking. In adopting substantive and confrontational sanctuary policies, San Francisco and Barcelona city officials have profited from opportune local contexts to do so: local policymakers and voters have progressive values; many community organisations support undocumented immigrants and advocate their interests in local politics; and available government resources make sanctuary policies possible. In such conducive local environments, city officials perceive substantive and confrontational sanctuary policies as practically viable and politically expedient (Bazurli 2019;Steil and Vasi 2014). Operating in a much less opportune local context than San Francisco, Houston city officials have adopted mostly symbolic and conformist sanctuary policies, despite a demographic need for more substantive and confrontational policies and a U.S. federal context thatsimilarly for San Franciscoprovides opportunities for developing them. Local constraints have been important in Milan, too. Nearly two decades of anti-immigrant local political leadership left a legacy of nativist policies, with Milan's divided political landscape making it challenging for community organisations to collaborate with city officials to embrace the city's many undocumented residents more fully.
There is need for additional research, first to test whether other city sanctuary policies can also be classified along the conceptual dimensions of policy content and policy harmony and whether these, too, can be explained by local and supra-local contexts. Importantly, we have offered initial inductive ideas on the drivers of variation in city sanctuary policies by leveraging our in-depth knowledge of cities we already knew well. Future studies, therefore, can build on, expand, and challenge our theoretical framework through systematic, including large-N comparisons, of sanctuary policies in other U.S. and European cities. Second, there are opportunities to refine our framework. Notably, our analysis captures cities with either substantive-confrontational or symbolic-conformist policies, suggesting a possible conflation between the policy content and policy harmony dimensions. How common then are city sanctuary policies that are either substantive-conformist or symbolic-confrontational, and how can local and supra-local contexts explain those? Relatedly, future studies may also want to refine our typology by recognising different gradients of content and harmony, while also using critical approaches to interrogate the possibly contested nature of these concepts. Third, our findings suggest that ideological differences between officials at different government levels may drive the adoption of confrontational city sanctuary policies in times of heightened polarisation over immigration, a dimension of city sanctuary policymaking that warrants further analysis as well.