Mapping European Law

R. Daniel Kelemen and Tommaso Pavone

Paper presented at the
Biennial Meeting of the European Union Studies Association, Boston, MA, March 5-7, 2015.

ABSRACT
This article constitutes the first systematic effort to analyze the subnational practice of European Union (EU) law across time and space. We derive eight empirically falsifiable  hypotheses  about  the  spatio- temporal structure of EU litigation from the extant literatures on European legal integration and policy diffusion and assess their ability to explain temporal and spatial variation in the use of the preliminary reference procedure by Italian courts. We then provide a series of empirical assessments of these hypotheses. We begin with a description of the spread of preliminary references across Italy from 1957 through 2013. We then conduct a series of statistical analyses by pairing EU litigation data  with subnational socioeconomic indicators to assess which variables best predict cross-regional variation in preliminary reference rates over the past two decades (1997-2012). Finally, we leverage GIS technology and elementary spatial statistics tools to more rigorously assess the spatial structure or clustering in the use of the preliminary reference procedure.

Introduction
Governance is a process that unfolds across space  and  time.  The  degree  to  which  a  government  can govern a polity in practice ultimately depends on the geographical extent and temporal consistency of its authority over its dominion. Does the central government exert its authority over the whole of its territory or over only a fraction of it? Does the central government exercise authority on an ongoing basis, or only sporadically? These are fundamental questions for any political system, particularly for federal or multi-level political systems in which multiple tiers of government may seek to exercise authority over the same territory. The “presence” of a regime in space and time is a thick concept that may be measured along multiple dimensions, with indicators ranging from the proliferation of its bureaucratic offices and officials, to the maintenance of military garrisons, to the collection of  taxes,  to  social  behaviors  that indicate broad recognition of the regime’s authority. Just which indicators are most relevant will vary

depending on the nature of the regime in question. Certainly, for regimes that seek to rule principally through law, measures of the reach of the regime’s judicial authority are crucial.
Scholars, European policy-makers, the European Court of Justice and the EU Treaties themselves all declare that the European Union (EU) is a community based on the rule of law.1 To the extent that the EU succeeds in governing its member states and private actors, it does so principally through judicial mechanisms. As one of us has argued elsewhere (Kelemen 2011), the EU relies heavily on a judicialized
mode of governance – termed ‘Eurolegalism’ - that enlists private litigants and national courts to help pursue the EU’s policy objectives. In the broadest sense, the EU can be conceptualized as what medieval historian Joseph Strayer (1970) called a “law-state” – a state constructed principally through the progressive expansion of state judicial institutions.2
Existing scholarly literature tells us  a great deal about the  crucial role the ECJ has  played in promoting the process of European integration and about the politics surrounding the construction of the EU’s legal system. Pioneering studies by Stein (1981), Weiler (1991), Burley and Mattli (1993), Slaughter, Stone Sweet and Weiler (1998), Stone Sweet (2000, 2004), Alter (2001), and others have demonstrated the importance of the ECJ’s expansive jurisprudence and of inter-court cooperation and competition in promoting legal integration.  These scholars,  and others such as Cichowski (2007)  and Kelemen (2011) also have highlighted the role of litigation brought by private parties in the construction of the EU’s legal order. The effectiveness of European law has always depended on the ECJ’s relationship with national courts who send it cases via the preliminary ruling procedure, recognize the supremacy of European law and apply European law and ECJ rulings domestically. As work by Alter (2001) and others has shown us, convincing courts in the original six member states to recognize the supremacy of European law and to send cases to the ECJ via the preliminary ruling procedure was a vital early step in the process of European legal integration. Since that crucial founding period, the ECJ, and more generally the EU, have worked to ‘socialize’ national judiciaries of new member states into the interlocking system of national and EU-level courts. Today thousands of judges across the twenty-eight states of the European Union are trained in European law, participate in EU-related judicial networks and are encouraged to engage with the EU courts in Luxembourg. Recent work by scholars such as Bobek

1 For scholarly views see for instance Kochenov (2009) and Pech (2009). For a view from EU leadership, see for instance, European Commissioner for Justice, Vivian Reding’s 2013 speech on the rule of law (Reding 2013). For references in EU law see Lisbon Treaty, Article 1a, and the ECJ’s ruling in Case 294/83 Les Verts v. Parliament [1986] ECR 1339, para. 23.
2 Also see Fukuyama (2012 p.271) and Berman (1983, p.406) on the concept of states built primarily through the
progressive subsumption of pre-existing local legal orders into the new overarching legal order of the larger polity being created. See also Kelemen (2014) conceptualizing the EU as a ‘law-state’.
also see Strayer 1970, pp.26-31). State builders sought to supplant the plurality of legal orders and judicial institutions that existed within their territories with uniform systems of law, and they largely succeeded. As Harold Berman (1983, p.406)

(2008) and Wind (2010) highlights the ongoing importance of – and challenges associated with – securing the participation of the judiciaries of new member states in the EU legal system.
And yet, for all that we know about the importance of the EU law to the process of integration, we know very little about actual penetration of the EU’s judicial order across space and time. To be sure, as we discuss below, some studies examine variations in the rate of references for preliminary rulings across EU member states. Chalmers and Chaves (2012) examine variations in the frequency of litigation
before the ECJ across various areas of EU law. More generally, many ‘impact studies’ seek to assess the actual extent to which EU law is applied across various member states.3 But for all the insight offered by this literature, it does not address fundamental questions about the actual reach of the EU’s judicial order across space and time, such as: Is EU law litigation concentrated around national capitals or in other particular geographic pockets, or is it dispersed throughout the territory of EU member states? How has
the geographic reach of EU law evolved over time? Has it expanded steadily or  followed  a  path- dependent pattern remaining clustered in particular locales? Answering these questions is vital because doing so will shed light on the true reach of the EU judicial order across the Union.
This paper seeks to address these questions by harnessing a methodology entirely novel to the field of EU law and politics and an original dataset of all preliminary references submitted by Italian courts to the ECJ from 1964 through 2013. We geocode the city location of every court that submitted a preliminary reference to the ECJ and use Geographic Information Systems (GIS) technology to analyze and explain the pattern of diffusion of these references across space and time. The aims of this paper are modest in some respects and extremely ambitious in others. Empirically, we limit our investigation to the study of one member state – Italy – and emphasize one indicator of the reach of the EU judicial order – the geographic location of Italian courts sending references for preliminary rulings to the ECJ. The conclusions we draw from the quantitative analysis of this data remain tentative. But while the immediate claims we make based on the paper are modest, the methodological turn and the theoretical ambition embodied in the paper – as well as the broader project of which the paper is a part – hope to offer a transformative perspective on the study of EU law.
We contend that the time has come for a spatial turn in the study of European law and governance. To understand the reach of the EU’s judicial order and of EU law more generally, scholars should consider the spatial dimensions of legal integration that have heretofore been ignored while remaining attuned to temporal changes in the practice of EU legal rules. First of all, considering the reach of EU law across space and time will provide a far richer picture of the reach of EU governance ‘on the ground.’  Secondly,  this  approach  offers  an  added  source  of  data  and  analytic  leverage  with  which  to

3   A   review   of   this   voluminous   literature   is   beyond   the   scope   of   this   article;   see   Treib   (2008) http://europeangovernance.livingreviews.org/Articles/lreg-2008-5/ for a review of this literature.

assess existing theories of legal integration. For instance, as we discuss below, many of the arguments in the literature that seek to explain variations in rates of  references  for  preliminary  ruling  across  EU member states generate observable implications regarding the litigation of EU law across regions within member states. Specifically, the same factors (i.e. trade exposure, social capital,  wealth,  domestic litigation rates) that are thought to lead some member states to generate more EU law litigation than others should correspondingly be expected to lead some regions within member states to generate more EU law litigation than others. By taking into account variation across regions within states, scholars can dramatically increase the ‘n’ in quantitative studies of EU law from 28 member states to the hundreds of sub-national regions within them, thereby gaining analytic leverage that will render quantitative analyses more robust.
Though this paper is limited to the study of preliminary references from one member state, it suggests important avenues for further research that we plan to pursue in subsequent work. Indeed, the same methods we apply to Italy can be used to study the geographic dispersion of references to the ECJ over time within other member states. Likewise, the use  of  geocoding  and  spatial analysis  using GIS could be used to study other aspects of the spread of the EU’s legal order, including the proliferation across space and time of law offices specializing in EU law, law faculties offering degree courses in EU law, or national courts citing ECJ decisions or otherwise referencing EU law in domestic proceedings.
The remainder of the paper is divided into three sections. Part I conducts a brief review of the existing literatures on European legal integration and policy diffusion and derives eight empirically falsifiable hypotheses about the spatio-temporal structure of EU litigation within Italy. Part  II  then provides a series of empirical assessments of these hypotheses. We begin with a description of the spread of preliminary references across Italy from 1964 through 2013. We then run a series of statistical analyses by pairing EU litigation data with subnational socioeconomic indicators to assess which variables best predict cross-regional variation in preliminary reference rates over the past  two  decades  (1997-2012). Finally, we leverage GIS technology and elementary spatial statistics tools to more rigorously assess the spatial structure or clustering in the use of the preliminary reference procedure. Our analysis uncovers several illuminating findings. First, although lower courts were the first Italian judicial institutions to refer cases to the ECJ, high courts have a substantially greater propensity to refer. Second, population levels and domestic litigiousness best explicate synchronic variation in preliminary reference rates since 1997, but there is evidence that the domestic litigation effect is causally heterogeneous. We also find strong evidence that EU litigation is spatially clustered and exhibits important issue-specific variation that will be missed if EU law is treated as an undifferentiated corpus of rules. Finally, Part III concludes.

The Diffusion of EU Law: Literature Review and Testable Hypotheses
A brief review of the literature on European legal integration and the diffusion of legal phenomena can serve as the basis to construct a number of empirically-testable hypotheses concerning the spread of EU law across space and time. The first sizable wave of scholarship on European legal integration in the late 1980s and 1990s was catalyzed by the reinvigorated interest in explaining the origins and development of the EU.4 Spurred by the perceived jumps towards supranationalism represented by the 1986 Single European Act and the 1993 Maastricht Treaty, political scientists reawakened the dormant international relations debate between neofunctionalists, who highlighted the self-reinforcing “spillover” processes spurring regional integration outside state control (Haas 1968), and intergovernmentalists, who held that integration remained firmly under the control of member states, acting in pursuit of their self-interests (Hoffmann 1966). Yet increasingly, political scientists found it impossible to ignore the contributions of legal theorists such as Eric Stein, Hjalte Rasmussen, and Joseph Weiler, who highlighted the role played by the ECJ in spurring the integration process – particularly in periods when member states were reluctant to do so (Stein 1981; Rasmussen 1986; Weiler 1986; 1991). Political scientists then developed a variety of political explanations of European legal integration focused on factors  such  as  the  ECJ's  strategic agency, its interactions with national governments, its ability to forge allegiances with domestic courts to further legal integration, the challenges member governments faced in controlling ECJ activism, and functional forces that encouraged judicial empowerment. Some scholars drew inspiration primarily from the neofunctionalist perspective (Burley and Mattli 1993, 1995; Stone Sweet 1999; 2000; Stone Sweet and Sandholz 1997) whereas others drew from a modified  intergovernmentalist  perspective  (Geoffrey Garrett 1992; 1995). Still others built on the neofunctionalist perspective but framed their analysis in the language of historical institutionalism, which helped it to engage in broader disciplinary debates in comparative politics and international relations  (Pierson 1996; Alter 1996; 2000; 2001).
By the late 1990s debates organized along intergovernmentalist vs. neofunctionalist lines seemed to exhaust themselves: On the neofunctionalist side, Slaughter and Mattli (1998: 179) wrote of their hope to close “the books on the neofunctionalist-intergovernmentalist debate” by promoting “a number of more specific studies on the role of individual litigants and national courts;'' On the intergovernmentalist side, Garrett, Kelemen, and Schulz (1998: 150) emphasized that they shared the neofunctionalists’ assumption that the ECJ is a “strategic actor” that is contingently able to “declare illegal national laws, regulations, or practices.” Just as the intergovernmentalist vs. neofunctionalist debate over EU legal integration subsided, a new wave of scholarship began to shift focus towards explaining cross-national  variation  in  the domestic demand for EU litigation. Despite these studies’ country-level focus, they nonetheless suggest a

4 There were of course a handful of earlier studies of EU legal integration from a social science perspective, such as those by Scheingold (1965, 1971).

number of hypotheses capable of explaining variations in engagement with the EU legal order (via the preliminary ruling procedure) across the subnational regions of EU member states, to which we now turn.

Judicial Empowerment
Weiler (1991) famously posited that the preliminary reference procedure was activated by the willingness of low-level domestic courts to litigate European law.  “The  legally  driven  constitutional  revolution,” argued Weiler, “was a narrative of plain and simple judicial empowerment [… as] the lower courts made wide and enthusiastic use of the Article 177 procedure [... thus] the constitutionalization of the Treaty of Rome [...] meant an overall strengthening of the judicial branch vis-à-vis the other branches of government” (Weiler 1991: 2426). Burley and Mattli (1993) echo Weiler’s thesis: The  reason  why domestic judges began to refer cases to the ECJ is that “the E.C. system gave judges at the lowest level powers that had been reserved to the highest court in the land” (Burley and Mattli 1993: 63). In a later article, Weiler further noted how the bourgeoning consumption of the preliminary reference procedure by lower courts spurred the gradual and reluctant acceptance of the ECJ’s supremacy doctrine by the French Conseil d’Etat, the Italian Constitutional Court, and  the  German  Federal  Constitutional  Court  (Weiler 1994: 521-524). Indeed, Stone Sweet and Brunell (1998) and Alter  (2001)  both  emphasize  that  the delayed referrals by domestic courts of final appeal is consistent with Weiler’s claims, since “the logic of empowerment did not apply to all national judges, such as those sitting on constitutional courts” (Stone Sweet and Brunell 1998: 69). To this end, Alter (1998) develops an inter-court competition argument suggesting that lower level courts used the preliminary reference procedure to circumvent superior courts in their own national judicial hierarchies who might otherwise have overturned their rulings on appeal. Despite the reiteration of similar arguments in later studies (see Conant 2002; Tridimas and Tridimas 2004; Bobek 2008), the judicial empowerment thesis has  not  found  unconditional  acceptance:  Golub (1996: 360), for example, argues that it cannot explain the comparative reluctance of British lower court judges to refer cases to the ECJ.
For our purposes, although the judicial empowerment argument does not suggest particular hypotheses with regard to cross-regional variation, it does suggest that in broad terms we should expect lower level courts to be more active users of the preliminary ruling procedure than higher level courts within national judicial hierarchies. Analysis of the courts that were the sources of preliminary references across Italy affords us with the opportunity to assess whether  the  judicial  empowerment  thesis,  and suggests our first hypothesis:

H1A:  Lower  court  judges  across  Italian  regions  should  be  the  most  active  consumers  of  the preliminary reference procedure.

Second, the judicial empowerment thesis also suggests that we should observe a particular pattern across time. This argument suggests that in the early days of legal integration, bold lower court judges who embraced the opportunity to review domestic statutes in light of supreme EU law should have been the first judicial actors to participate in the preliminary ruling system, whereas higher courts should have only conceded to participation in the EU legal system later, after the pattern of references from lower courts had  been established. This causal narrative suggests a corollary to our first hypothesis:

H1B: Over time, the share of Italian references coming from high courts should increase.

Trade
In their pioneering study, Stone Sweet and Brunell (1998) posited that increased national levels of transnational economic exchange lead to increased demand for ECJ dispute resolution, activating a “virtuous” cycle. Specifically, “levels of preliminary references will vary” posit Stone Sweet and Brunell, “across member states, court systems, and legal domain – as a function of the intensity of transnational activity,” where “intra-EC trade [serves] as a proxy for transnational exchange” (Stone Sweet and Brunell 1998: 75). Their finding of a positive correlation between the magnitude of a country's exports and its preliminary reference rates was later corroborated by Fligstein and Stone Sweet (2004), Tridimas  and Tridimas (2004), and Carrubba and Murrah (2005). Importantly, the functional logic behind the argument linking increased levels of trade to increased rates of references from national courts to the ECJ should extend to the subnational level: The same causal logic that suggests that states that trade more should generate more references to the ECJ would in turn suggest that regions within states that trade more should generate more references. This leads to the following hypothesis:

H2: The greater the share of trade in a region’s economy, the higher the rate of references to the ECJ originating from courts in that region.

Population and Domestic Litigiousness
In a recent paper, Vink et al. (2009) posit that the strong correlation between trade levels and reference rates uncovered by Stone Sweet and Brunell (1998) suffers from omitted variable bias. Specifically, “we suggest two more intuitive factors: population size and litigation rates. First, bigger member states will make more references than small member states simply because there are more court cases as such and also more courts and judges that can refer questions. Second, some states are more litigious than others, due to legal culture, the availability of systems of alternative dispute resolution, or legal aid” (Vink et al.

2009: 13). The observable implication of this argument, then, is that any statistically significant correlation between trade levels and reference rates will disappear when controlling for population size and domestic litigation rates. Vink et al. (2009)’s country-level analysis finds empirical support for this hypothesis, where both population size and litigation rates exhibited a strong and positive effect on use of the preliminary reference procedure. On the other hand, Golub (1996: 368-375) underscores that if population size is the primary predictor of preliminary reference rates, then British judges should refer substantially more cases to the ECJ than they do in practice, and he further highlights  that  several qualitative studies have “found that differences in societal litigiousness and internal national  judicial structure were either minimal or inconsequential” in explaining reference rates. In this light, a more fine- grained, subnational analysis may allow us to assess the validity of Vink et al. (2009)’s claims, leading to the following two hypotheses:

H3: The more populous a region, the higher the rate of references to the ECJ originating from courts in that region.

H4: The greater the overall rate of litigation within a region, the higher the rate of references to the ECJ originating from courts in that region.

Social Capital and Civic Engagement
Cichowski (2007)’s analysis of domestic actors’ use of the preliminary reference procedure builds upon Epp (1998) to offer the important caveat that the litigation of EU law is contingent upon the plaintiffs’ ability to garner the necessary civil society support. Underlying these arguments is a longstanding claim, popularized by Putnam (1994), that patterns of civic engagement and associational life bolster the effectiveness of democratic institutions. Importantly, Putnam’s empirical study revealed substantial subnational variation in social capital levels across the Italian peninsula, which offers us an excellent opportunity to assess whether civic engagement may explain inter-regional variation in preliminary reference rates. This leads to our fifth hypothesis:

H5: The greater the levels of civic engagement within a region, the higher the rate of references to the ECJ originating from courts in that region.

Material Resources
The resource mobilization approach to the study of social movements emphasizes that the mobilization of material resources is a necessary  condition for social movement formation  (McCarthy and  Zald 1977; Jenkins 1983). Drawing on this approach, Epp’s (1998) comparative study of social activists’ ability to

leverage law to promote progressive social change emphasizes the degree to which prospective plaintiffs are dependent on the existence of a “litigation support structure.” Cichowski (2007) incorporates this perspective within her analysis of EU law litigation and emphasizes that, in addition to the presence of social capital, material resources and organizational structures are necessary to support litigation. In part, the concept of litigation support structures is based on  the  existence  of  civic  organizations  that  can support litigation, and thus overlaps with measures of social capital and civic engagement discussed just above and captured in hypothesis 5. But the concept of material resources also  has  a  more  purely economic dimension: Ceteris paribus, wealthier individuals should be better able to invoke EU legal provisions in court. Indeed, the resource mobilization literature stressed the support of economic elites for the advancement of any social movement, for they possess the resources necessary to support a movement’s organizational and litigation strategies. Conant  (2002)  and  Tridimas  and  Tridimas  (2004) make similar claims: “private litigants who have access to the required financial resources… will be privileged” in using the procedure (Tridimas and Tridimas 2004: 133). We believe that GDP per capita can serve as a plausible measure of the “resource stock” available to prospective EU litigants, and this provides the basis for our sixth hypothesis:

H6: The greater the levels of GDP per capita within a region, the higher the rate of references to the ECJ originating from courts in that region.

Issue-Specific Variation
One of the most illuminating claims of Stone Sweet and Brunell (1998: 88) that has yet to be systematically assessed is that intra-issue variation in country-level reference rates exists. With respect to social provisions, for example, “UK judges refer far more cases per year to the ECJ than do judges in any other member state,” despite the fact that five states – Germany, France,  Italy,  the  Netherlands,  and Belgium, in this order – refer more cases to the ECJ overall (Stone Sweet and Brunell 1998 88; 74). Sigafoos (2012: 504) corroborates this thesis by positing  that  the  UK’s  higher  level  of  social-policy related references compared to France can be traced to the latter’s comparatively more generous “Bismarckian welfare state,” which is “very generous to insiders, who are seldom motivated to challenge the system.” While the organization of the welfare state is likely to engender variation focused at the country level, it is certainly plausible that analyzing the litigation of an undifferentiated corpus of EU law would mask important  issue-specific variation at  the subnational  level. For  example,  we might  expect trade-rich  regions  to  litigate  EU  common  market  provisions  more  frequently  than  EU  social  policy

provisions, and we might expect the opposite pattern of litigation in unemployment-prone regions. This logic suggests a seventh empirically-testable hypothesis:

H7:  The  subnational  use  of  the  preliminary  reference  procedure  will  exhibit  issue-specific variation across time and space.

Spatial Clustering
Although the EU integration literature has yet to systematically engage with the burgeoning scholarship on the diffusion of judicial practices and public policy, we believe this is an opportune time to “bring diffusion in,” as it were. On the basis of a survey of over thirty different diffusion mechanisms uncovered by the extant literature, Elkins and Simmons (2005: 35) conceptualize diffusion as “a set of processes characterized by interdependent, but uncoordinated, decisionmaking [...] In other words, uncoordinated interdependence.” The authors are joined by Berry and Baybeck (2005) in uncovering two broad classes of mechanisms posited by the literature: (1) learning and (2) adaptation to a more competitive environment.5 Amongst public law scholars, these mechanisms have been discussed most extensively in the American literature. With regards to learning mechanisms, scholars highlight that inter-court proximity, greater judicial professionalism/prestige, the presence of shared issue-specific knowledge, integrated legal reporting mechanisms, and common cultural linkages facilitate the diffusion of  legal precedent and litigation via various forms of emulation (Canon and Baum 1981; Caldeira 1985; Moser and Turbek 2006; Linos 2006). Evidence of competition-induced legal development has been somewhat scarcer. Shipan and Volden (2008) interpret their finding that American cities are reluctant to adopt anti- smoking laws if neighboring cities have not already done so as supportive of  competition-induced diffusion, and Moser and Trubek (2006: 1471) broadly claim that “agents in competitive environments are more likely to innovate and imitate than agents facing weaker competitive pressures.” Linos (2006), however, leverages a case study of the development of American corporate law to argue that legal innovations do not converge towards more efficient focal point solutions via competition but are instead spurred by learning-induced mimicry.
While scholars clearly disagree with respect to which underlying causal mechanisms best explain the spread of governance practices across space and time, most of the diffusion scholarship generates the same observable implication: Namely, that proximity facilitates the diffusion of policy and judicial practices. The causal mechanisms posited to explain diffusion, such as competitive pressures, information

5 Elkins and Simmons (2005) and Shipan and Volden (2008) also note that diffusion can be induced by a hegemonic power via coercion; we do not consider this mechanism here as the lack of a supranational coercive apparatus in the EU precludes this from being a germane diffusionary mechanism.

diffusion, and emulation processes, are likely to be facilitated by spatial proximity. We do not propose to untangle the causal mechanisms that underlie the spatial clustering of governance practices. Instead, we extend the observable implications of the diffusion literature by proposing a final hypothesis:

H8:  The  most  active  judicial  consumers  of  the  preliminary  reference  procedure  should  be spatially clustered together.

The Litigation of EU Law in Italy Across Time and Space
In this  section,  we empirically assess the foregoing  eight hypotheses  by describing and analyzing the spatio-temporal structure of EU litigation across Italy. Italy is particularly well-suited to this endeavor given its stark inter-regional socioeconomic diversity. Throughout, we provide supportive evidence for, and underscore the limitations of, existing theories and suggest fertile avenues for future research. We begin with some descriptive statistics concerning the use of the preliminary reference procedure by Italian courts. We then conduct statistical analyses to shed light on the economic, civic, and social determinants of EU litigation in the past 15 years. Finally, we probe the degree to which the litigation of EU law tends to be issue-specific and spatially clustered.

The Spatio-Temporal Structure of EU Litigation
In the only empirical study to date regarding the use of the preliminary reference procedure in Italy, Reale and Borracetti (2008: 3; our translation) highlight that while preliminary references comprise an “very considerable percentage” of the ECJ’s caseload, at the subnational level  references  “comprise  a  very minimal fraction [of litigation] compared to the flow of [domestic] lawsuits registered annually.” Ferrari (2011: 100) adds that “knowledge of EU law in Italy, on behalf of judges as well as lawyers, is contingent in practice and is distributed like a leopard’s skin.” In other words,  we  should  not  assume  a  dense, uniform, and monotonically increasing pattern in the use of the reference procedure across Italy, despite what we might be tempted to extrapolate from the fact of the ECJ’s ever-increasing caseload. To this end, we constructed an original dataset of all references submitted to the ECJ by Italian courts from the entry into force of the Treaty of Rome in 1957 through December 2013 (n=1,223).  The  references  were geocoded based on the city location of the referring court to enable mapping using Geographic Information Systems (GIS) technology.
Before assessing the foregoing hypotheses, it is useful to begin with some time-series descriptive statistics. Figure 1 displays the number of preliminary references submitted by Italian courts, aggregated by decade. We plotted data at the national level as well subsets from northern and southern Italy only,

since Italy’s north-south socioeconomic divide may reveal region-specific patterns that are masked when data is aggregated nationally.6 Figure 1 demonstrates that the national number of preliminary references rose monotonically through 2003, but over the past decade there has been a slight drop in the total number of references submitted by Italian courts. Yet the Figure also reveals that the source of this decrease lies in a decline in northern references since 2003. Although southern Italian courts hardly submitted any references pre-1993, over the past decade they have been almost as active in referring cases to the ECJ as their northern counterparts.

Figure 1: Preliminary References Submitted by Italian Courts (by Decade), 1964-2013

Beyond measuring the quantity of references submitted by Italian courts, we can also measure the degree of dispersion of said references – that is, the proportion of provinces that are home to a court that referred at least one case to the ECJ. Figure 2 displays these data aggregated by decade. At the national level, there has been a steady increase in the proportion of provinces with a referring court, although the monotonic rise pre-2003 has slightly stalled since. Over the past decade, 53% of Italian provinces were home to a referring court. The figure also highlights that the dispersion of references across northern  Italy  has remained relatively steady since the 1980s (increasing from 50% in the 1984-1993 period to 58% in the 2004-2013 period (a 16% increase)) but has risen dramatically across southern Italy  during  the  same temporal frame (rising from 16% to 41% (a 115% increase). Thus although the use of the preliminary

6 Following ISTAT conventions, we group Italian regions as follows: Piemonte, Lombardia, Trentino-Alto Adige, Emilia-Romagna, Friuli-Venezia Giulia, Liguria, Valle d’Aosta, and Veneto: North; Abruzzo, Basilicata, Calabria, Campania, Molise, Puglia, Sardegna, and Sicilia: South; Lazio, Marche, Toscana, and Umbria: Center.

reference procedure has been most frequent and diffuse across northern regions, over the past two decades there has been a relative equalization in the frequency and dispersion of preliminary references.

Figure 2: Proportion of Provinces with a Referring Court (by Decade), 1964-2013

Let us now proceed to an evaluation of H1A and H1B: is there evidence of the “judicial empowerment” thesis of Weiler (1991; 1994) and elaborated by Stone Sweet and Brunell (1998) and Alter (2001)? In other words, have lower courts been the most active consumers of the preliminary reference procedure, and have mid-level and high-courts become more active over time? Figure 3 displays the longitudinal pattern of yearly references submitted by these three court types (Appendix A provides the displays this same information in the form of proportion of years references submitted by each court type). Following Stone Sweet and Brunell (1998), we classify a lower court as a court of first instance, a mid-level court as a court possessing appellate jurisdiction, and a high court as a court possessing final jurisdiction (for a more detailed description of the Italian judicial hierarchy, see Appendix B). What emerges is the fact that most references have indeed originated from lower courts, yet over  the  past  few  years  a  substantial number of references have been submitted by Italian high courts, particularly the Court of Cassation and the Council of State.
In interpreting these trends, we should emphasize the fact that the number of lower Italian courts numbers in the thousands, whereas there are only a half-dozen courts with final jurisdiction, so it can hardly be viewed as surprising that more cases would originate with lower courts. Furthermore, while most preliminary references do indeed emerge from courts of first instance, the average lower court does

not have a greater propensity to refer a case to the ECJ than  the  average  high  court.  Consider,  for example, one measure of propensity to refer, namely the average number of references submitted by court type. From 1964 through 2013, there have been 926 references submitted by 267 distinct lower courts (an average of 3.47 references per lower court), 63 references submitted by 30 distinct mid-level courts (an average of 2.1 references per mid-level court), and 229 references submitted by 6 high-level courts (an average of 38.17 references per high-level court). In short, courts with final appellate jurisdiction appear substantially more likely to refer a case than are low-level courts. This evidence is supportive of H1B but not H1A: That is, lower courts do not have a greater propensity to refer cases to the ECJ, but it is true that in the first decade and a half following the ratification of the Treaty of Rome, most Italian references originated within courts of first instance, and over time the share of cases coming from higher courts has increased.

Figure 3: Yearly Preliminary References by Court Type, 1964-2013

Although the foregoing analyses are well-suited for uncovering the temporal structure of EU litigation, they are inadequate for assessing the spatial-structure of the same phenomenon. If it is true, as Ferrari (2011) posits, that knowledge of EU law in Italy is distributed like a leopard’s skin, then perhaps we will uncover a similar spatial pattern in the distribution of preliminary references. To this end, we georeferenced the city location of all cases referred to the ECJ by Italian courts and mapped these point data using Geographic Information Systems (GIS) software. Figures 4 and 5 display the revealing spatial structure of EU litigation from 1964 through 2013.

Figure 4: The Spatial Distribution of Preliminary References, 1964-1983

Figure 5: The Spatial Distribution of Preliminary References, 1984-2013

What is the general story told by Figures 4 and 5? In the 1960s, only a few courts across northern Italy and the capital city of Rome submitted references. In the 1970s, a steady increase in the number and dispersion of references across northern regions occurred, and the frequency of referrals  in  Rome increased substantially. This pattern became entrenched in the 1980s and the 1990s, with the majority of references originating from the provinces of Venice, Milan, Genova, and Rome. However, in the 1990s we can discern the ‘awakening’ of southern courts, as the number of references as well as their territorial coverage across the Mezzogiorno increased sharply. This equalizing trend has continued over the past decade, and indeed if we simply referred to the spatial distribution of references in the 2004-2013 period

one would be hard-pressed to discern the north-south divide in EU litigation that was so vivid during the three decades following the ratification of the Treaty of Rome.
The fact that northern courts were the first and most frequent referrers of cases to the ECJ is unsurprising, as several of our hypotheses would predict that northern courts would be particularly active consumers of the preliminary reference procedure.  Northern regions are integrated within networks of inter-European trade (corresponding to H2), and in the postwar era they have benefitted from the presence of industrial districts endowed with a “strong civicness  –  efficient  institutions,  informal  knowledge, shared ethics and cooperative informal rules…and homogenous in  production”  (corresponding  to  H5) (Felice and Vecchi 2012: 25). In such an economically interdependent space populated by  civic  and economic organizations, the litigation of EU law is more likely to be supported by resource-rich “repeat players” (corresponding to H6) (Galanter 1974) with the requisite knowledge of EU legal provisions. For example, Genova’s relatively high levels of litigation of EU law “is easily explained by the fact that litigation was initiated by the same law firm” (Ferrari 2011: 100). The relatively more efficient performance of state institutions across northern Italy, extensively documented by Putnam (1994)’s study, also implies that judicial institutions are more likely to operate effectively, and the steady flow of cases implicating EU law provides them with frequent opportunities to gain greater expertise in the adjudication of EU law. In short, the greater concentration of trade and social capital across northern Italy  likely contributed to the emergent practice of EU law in the 1960s and 1970s, consistent with H2, H5, and H6.
We might wonder, however, what explains the subsequent dissipation of a north-south divide in the litigation of EU law. It is tempting to assume that this process is epiphenomenal of a gradual socioeconomic equalization across Italian regions. This would  occur  if  the  economic  and  civic development of southern regions has gradually converged with their northern counterparts. Yet, a series of historical and econometric studies by the Bank of Italy and university researchers demonstrate a remarkable resilience of the north-south socioeconomic divide (the questione meridionale, as it is known in Italy) in the postwar period, in spite of state efforts via the Cassa per il Mezzogiorno program to boost southern employment  and  entrepreneurship  via  infrastructure  development  and  favorable  taxation policies. With respect to measures of social capital, including political participation in elections, civic volunteerism, and social trust, the Bank of Italy concludes that through 1998 and  2001  social  capital remained concentrated in northern Italian regions, and a macro-historical comparison of political participation in 1921 and 2001  detects  negligible  change  in  the  disproportionately  higher  participation rates in northern communities (Banca D’Italia 2010: 19-20). The same study highlights that “from the second half of the 1970s the Mezzogiorno does not demonstrate any  significant  convergence”  with northern regions (Banca D’Italia 2010: 2). Another longitudinal study concludes that the north-south socioeconomic  divide  has  remained  an  enduring  feature  of  the  Italian  landscape  at  least  since  Italy’s

unification in 1861 (Felice and Vecchi 2012: 22; 26). And yet another report underscores that “while other late developing European regions have begun a process of converging  towards  the  European average, the Mezzogiorno does not gain any ground vis-à-vis the center-north” (Banca D’Italia 2009: 7). Finally, although northern and central Italian regions  have  seen  population  growth  in  the  past  fifteen years, the southern population has remained stagnant (see Appendix C). In short,  neither  growing southern trade (H2), nor population change (H3), an increase  in  civic  engagement  (H5),  or  economic growth (H6) explains the recent equalization in preliminary reference rates across the Italian peninsula.
Alternatively, we might posit that the growing litigation of EU law across southern Italy evidences the recent  spike in southern litigiousness,  following Vink et  al.  (2009) and H4.  Yet in  the postwar period the problem for southern Italy has not been a reluctance to litigate but the longstanding overlitigiousness of southern society (Carmignani and Giacomelli 2009; 2010). As early as the 1950s “the universities of Rome, Naples, Palermo and Messina turned out law graduates in their thousands” despite their “poor job prospects” (Ginsborg 2003: 146), suggesting that the notorious oversupply of southern lawyers (Camarda and Pierleoni 2014) is an enduring feature of the Mezzogiorno’s sociolegal landscape.7 The south is also home to a disproportionate share of the state’s magistrates (Ferrari 2011), but notably the territorial distribution of the magistracy has largely remained fixed in the postwar period. Finally, Appendix D shows that litigation rates before southern administrative courts has not risen over the past two decades – in fact, the number of cases has  decreased slightly since the mid  1990s. In short, H4 similarly fails to explicate the temporal structure of EU litigation in the Italian south.
A more likely equalizing force may be a mechanism stressed by the policy diffusion literature, namely, the diffusion of information. The late 1980s witnessed the implementation of the EU’s regional policy aimed at reducing regional socioeconomic disparities via the distribution of structural funds. This policy led to what two scholars called a “paradigm  shift”  in  the  Mezzogiorno’s  social  policymaking process (Bull and Bauder 2004: 1061). A partnership between the European Commission, the central government, and southern regional governments was institutionalized, and between 1996 and 2000 a Mezzogiorno Development plan was drafted to, inter alia, bolster “networks and communications” across southern regions. Southern regional governments were, for the first time, delegated substantial fiscal responsibility, capable of managing over 70% of the plan’s total resources.  Further,  the  Commission required the institutionalized inclusion of “social actors” and the forging of “partnerships” at both the plan’s drafting and implementation stages (ibid: 1062). For the first time an EU development policy was specifically targeted to southern regions and had induced the active participation of local and regional actors   (Tedesco   2006).   This   process   of   “Europeanization”   “diffused   the   norms   and   instruments

7 Indeed, Naples alone is home to approximately the same number of lawyers as in all of the United Kingdom (Buonanno and Galizzi 2010: 2).

incorporated in the instruments” of the Mezzogiorno Development plan to local policymakers and civil society actors (Bull and Bauder 2004: 1069; Tedesco 2006: 90). As these hybrid institutions were forged, it is likely that a substantial share of southern legal professionals became aware of EU legal provisions for the first time. While this evidence does not assess the validity of H7 directly, it does support our argument that the EU legal integration literature needs to pay greater attention to diffusion mechanisms.

The Determinants of the Subnational Litigation of EU Law
Subnational use of the preliminary reference procedure also allows us to statistically assess whether the correlations between preliminary references  and  various  economic,  demographic,  and  sociolegal indicators highlighted by the second wave of EU legal integration scholarship also hold subnationally. These types of analyses seek to unearth the degree of functional responsiveness of EU law to variant socioeconomic conditions. To undertake this task, data were gathered to  assess  arguments  positing  a positive impact on EU litigation of population size (H3) (Vink et al. 2009; Sigafoos 2012), of the material resources to support litigation (proxied here by GDP per capita, as per H6) (Epp 1998; Tridimas and Tridimas 2004; Sigafoos 2012), of social capital and civic engagement (H5) (Putnam 1994; Cichowski 2007), of intra-European trade (H2) (Stone Sweet and Brunell 1998a), and of domestic litigation rates (H4) (Vink et al. 2009). Measures for the foregoing variables were obtained from the Italian Statistical Service (ISTAT) at the regional level, as they were not consistently available for  a  smaller  unit  of territorial organization. Further, data were only consistently available post-1997, which allows us to focus on a single historical  period but  precludes us from leveraging this analysis for explicating  diachronic variation in EU litigation rates from 1964 through 1997 to corroborate our assessments in the previous section. In other words, this analysis is better suited to explaining cross-sectional, or synchronic, variation in reference rates.
It is important to note that Ordinary Least Squares (OLS) regression is likely to be an inappropriate model for assessing the determinants of preliminary references at the subnational level. Not only is our dependent variable – the number of yearly regional references – discrete rather than continuous, but at the subnational level there are likely to be many jurisdictions that in a given year submit no references to the ECJ. That is, the dependent variable is likely to be overdispersed and right- skewed, meaning that it will not possess constant variance. Appendix E, which captures the distribution of region-level preliminary references, corroborates this assumption. Further, the yearly  number  of regional references is a limited dependent variable, meaning that it cannot take on negative values, which violates the OLS assumption that the dependent variable is unbounded. Indeed, OLS regression is inappropriate  for  the  analysis  of  count  data.  Event  count  models  like  Poisson  regression  are  more

appropriate analytic tools in this case. However Poisson models assume that the variance of the dependent variable is approximately equal to the expectation of  the  dependent  variable,  and  in  our  case overdispersion in the dependent variable causes its variance (=19.33) to be almost ten times larger than its expectation (=2.09). For overdispersed count data, either a zero-inflated Poisson regression or a negative binomial regression are the most appropriate statistical models. However, zero-inflated Poisson models assume that the processes that generate counts of zero for the dependent variable are different from those that generate non-zero counts; we have no reason to make this assumption, and consequently we use a negative binomial regression model.
We ran four different negative binomial models regressing the yearly number of regional preliminary references (Yearly PRs) on Export Share (the  percentage  of  national  exports  for  a  given region in a given year), logged population, domestic litigation (proxied by the yearly number of cases lodged before a region’s Tribunale Amministrativo Regionale (TAR), or regional administrative court of first instance), civic participation (measured by the number of survey respondents in a given region in a given year who participated in a cultural, recreational, or other civic activity in the previous 12 months), and logged GDP per capita. The first model comprises data for all of  Italy.  However,  because  the dynamics spurring litigation in Rome are likely to be sui generis, if only because it is home to Italy’s supreme courts, we ran a second model for Italy excluding observations from the Lazio region where Rome is located. We believe this second model is going to be more accurate for estimating national-level correlations. Finally, to account for the possibility  of region-specific causal heterogeneity, we ran two final models restricting observations to just northern regions (Model 3) and southern regions (Model 4). The results of these analyses are captured in Table 1.
Table 1 showcases some surprising results. First, contrary to H2 and Stone Sweet and Brunell (1998)’s claims that the number of preliminary references closely correlates with the level of economic exchange, a region’s export share is not a positive predictor of the yearly number  of  region-level references when controlling for the effect of the other covariates. In fact, across northern Italy there is a negative correlation between export activity and EU litigation that approaches statistical significance (p<0.10). These results remain when the dependent variable  is  limited  to  common  market  references which we would expect to be most closely associated with export levels, specifically references related to EU competition, taxation, free movement of goods and services, and establishment provisions (see Appendix F). To be sure, these results should not be interpreted as establishing that trade-prone regions are not more likely to litigate EU legal provisions (as we will demonstrate  in the following section). However, they do cast doubts about whether export activity per se is systematically causing variant subnational use of the preliminary reference procedure.

Table 1: The Determinants of Region-Level Yearly Preliminary References, 1997-2012

	1: Italy
DV: # Yearly PRs	2: Italy (w/o Lazio)
DV: # Yearly PRs	3: North Italy
DV: # Yearly PRs	4: South Italy
DV: # Yearly PRs	

Export Share	-0.0587****	
-0.0331	-0.0883*	
0.397	
	(-3.46)	(-1.52)	(-1.72)	(0.98)	

ln(Population)	1.249****	1.342****	0.639****	2.078***	
	(6.34)	(6.21)	(3.30)	(3.03)	
Domestic Litigation	0.0864****	-0.0247	0.641***	-0.204***	
	(3.79)	(-0.49)	(2.61)	(-2.98)	
Civic Participation	0.0127	0.0374	0.0285	-0.0486	
	(0.45)	(1.10)	(1.00)	(-0.28)	
ln(GDP/capita)	2.503****	1.016	0.0652	0.159	
	(5.27)	(1.28)	(0.04)	(0.08)	
(Intercept)	-34.83****	-20.69***	-6.025	-17.72	
	(-6.75)	(-2.62)	(-0.34)	(-0.78)	
N	218	207	87	88	
t statistics in parentheses
* p < 0.10,  ** p < 0.05,  *** p < 0.01,  **** p < 0.001

Notes: The dependent variable is the number of yearly references at the regional level. The analysis leveraged heteroskedasticity-robust standard errors for all models. Measures for covariates were obtained from ISTAT: ln(Population) is the log of a region's yearly population (in 1000s); ln(GDP/cap) is the log of GDP per capita in any given region-year (in euros); Export Share is the percent of yearly national exports originating from a region; Civic Participation is the percent of respondents who participated in cultural, recreational, and other civic organizations in the previous 12 months; Unemployment Rate is the yearly percent of the working-age population aged over 15 years that is unemployed; and Domestic litigation is the yearly number of cases lodged before a region's administrative court of first instance (TAR).

Secondly, and consistent with H3, population appears to be a consistent and significant predictor of EU litigation: Across all model specifications, the logged population covariate is positively and significantly correlated with the yearly number of region-level references (p<0.001). This corroborates the findings of Vink et al. (2009) and Sigafoos (2012). Thirdly, levels of social capital, proxied by civic participation rates, are not a significant predictor of preliminary references across all model specifications, in contravention with the expectations of H5. This calls into question whether extensions of Putnam (1994)

or Cichowski (2007)’s emphasis on civic associationalism can be leveraged to explicate systematic subnational variation in EU litigation rates. Fourthly, logged GDP per capita, which proxies the presence of the material resources necessary to support litigation, appears uncorrelated with EU litigation in all models except Model 1.
Perhaps the most interesting result, however, concerns the relationship between domestic litigation before regional administrative courts and EU litigation rates (as posited by H4). Although no significant relationship appears in Model 2 when data is aggregated at the national level (excluding the Lazio region), this is a byproduct of causal heterogeneity engendered by the Italian north-south divide. Specifically, Model 3 reveals a positive and statistically significant (p<0.01) relationship between domestic litigation levels and the yearly number of region-level references across northern Italy, as Vink et al. (2009) predict. Yet Model 4 highlights that the opposite relationship holds across southern Italy, namely a negative and equally significant (p<0.01) relationship between the two variables. To facilitate the interpretation of the regression results and to visualize the presence of a causally heterogeneous effect of domestic litigation on EU litigation rates, Figures 6 and 7 plot the predicted yearly number of regional preliminary references across various levels of domestic litigation (holding all other covariates at their means) across northern and southern regions.8

Figure 6: Predicted Number of Preliminary References by Domestic Litigation Levels (Northern Italy)

8 The different values for the X-axes in Figures 6 and 7 are a function of the different average yearly number of cases before regional administrative courts in the north and south: For the north, the mean is approximately 2,000 (standard deviation of 1,700); for the south the mean is approximately 4,000 (standard deviation of 4,500).

Figure 7: Predicted Number of Preliminary References by Domestic Litigation Levels (Southern Italy)

Overall, these results underscore the fact that country-level relationships between various indicators of economic and sociolegal conditions and EU litigation cannot be assumed to hold at the subnational level, and that findings based on national averages may mask divergent patterns at the subnational level. At the regional level in Italy, not only does the positive correlation between export activity and reference rates posited by Stone Sweet and Brunell (1998) (as well as Fligstein and Stone Sweet (2002), Tridimas and Tridimas (2004), and Carrubba and Murrah (2005)) disappear, but there is evidence of a spatially heterogeneous effect of domestic litigation levels on reference rates. Undoubtedly, then, a “local turn” in the empirical study of the functional responsiveness of the preliminary reference procedure appears to be a particularly fertile avenue for future research.

Issue-Specific Litigation and Spatial Clustering
A weakness of the type of statistical analysis conducted in the previous section is that it fails to account for issue-specific litigation of EU law (as posited by H7) and the degree to which it is spatially clustered (as posited by H8). In other words, by treating EU law as an undifferentiated corpus of legal provisions and failing to provide a nuanced assessment of the geographic distribution  of  its  practice,  statistical analyses to date may mask important issue-specific variation in the spatial structure of EU litigation. To assess this possibility, we code preliminary references based on the subject-matter classifications of the ECJ’s  CURIA  database.  These  non-mutually  exclusive  categories  were  then  grouped  under  13  issue

headings, such as taxation and environmental policy, following Stone Sweet and Brunell (1998). We subsequently leverage GIS to uncover the spatial structure of issue-specific use of the  preliminary reference  procedure.
Perhaps the most significant economic transformation to diffuse across Italy in the post-war era has been the gradual decline of agricultural activity as a mode of production, particularly following the “economic miracle” of the 1960s (Ginsborg 2003). As such, H6 would predict a corresponding decline in the litigation of EU legal provisions relating to the Common Agricultural Policy (CAP), which provides market-supporting mechanisms for farmers to adjust to climate-based exogenous shocks, income support via direct payments, as well as various rural development programs (Commission 2014: 7). Indeed, the share of yearly preliminary references related to agriculture has  continued  to  drop  steadily  since  the 1970s: From 1970 through 1980, CAP-related references consistently comprised between 60 and 80% of all Italian references; between 2000 and 2010, by contrast, this proportion had dropped to around 10%, as displayed in Figure 8.

Figure 8: Share of Yearly Preliminary References Related to EU Agricultural Provisions, 1970-2013

Yet if H7 is correct, there should be some issue areas within EU law that are consistently litigated across time – that is, the temporal structure of preliminary references rates should vary by issue area. One bundle of EU rules whose litigation should remain constant includes EU taxation provisions, which “established as a main priority for tax policy that of addressing the concerns of individuals and businesses operating within the Internal Market by focusing on the elimination of tax obstacles to all forms of cross-border economic  activity”  (Commission  2014b).  We  might  expect,  for  example,  that  the  expansion  of  inter-

European trade would generate an increase in the number of references related to taxation provisions. Consequently, despite the rise in the total number of yearly references submitted to the ECJ by Italian courts, the share of taxation-related references should remain steady or perhaps even increase, in contradistinction to agriculture-related references. Indeed, Figure 9 demonstrates that this is the case.

Figure 9: Share of Yearly Preliminary References Related to EU Taxation Provisions, 1970-2013

Furthermore, to assess H7 we should probe the spatial structure of issue-specific litigation. Consider, for example, the spatial distribution of EU free movement of goods and services provisions, which comprise the heart of the Commission and the ECJ’s liberal regulatory framework for the common market. Articles 28 and 29 of the Treaty of Rome famously declare that “quantitative restrictions on imports [and exports] and all measures having equivalent effects shall be prohibited between Member States” absent compelling countervailing public safety interests (see Commission 2010). As Figure 10 highlights, the litigation of these rules is concentrated across highly industrialized northwest Italy,  particularly  in  Lombardy  and Liguria, the latter being home to Genova, which is Italy’s largest port. In fact, for many of these cities free movement references comprise over 75% of the total number submitted since 1964. A similar pattern should emerge vis-à-vis the aforementioned EU taxation provisions, as the high density of import-export companies engaged in inter-European trade should encourage the invocation of these EU rules  to challenge protectionist or business-stifling domestic taxation policies. Once again, Figure 11 highlights that this is the case. Overall, this evidence provides strong evidence that the spatial-temporal structure of EU litigation varies by issue area, strongly corroborating H7.

Figure 10: Spatial Distribution of Free Movement of Goods and Services-Related References, 1964-2013

Figure 11: Spatial Distribution of Taxation-Related References, 1964-2013

Although the clustering of free movement and taxation references across northwest Italy is evident, suggesting that H8 is plausible, there exist spatial statistics tools that allow us to measure whether said clustering is statistically significant. Such an analysis allows us to more conclusively assess the validity of H8. The most common measure of local spatial autocorrelation is the Local Moran’s I (Cho et al. 2008). The Local Moran’s I identifies whether high or low values of a particular variable are clustered spatially or whether they significantly differ from their neighboring environment. That is, the Local Moran’s I can be used to identify “high-high” clusters (where high values of a particular variable tend to be geographically clustered together), “low-low” clusters (where low values of a particular variable tend to be clustered together), “high-low” outliers (where a high value  is  surrounded  by  significantly  lower values) and “low-high” outliers (where a low value is surrounded by significantly higher values).
To illustrate the value of this measure of spatial autocorrelation, Figure 12  shows  the  Local Moran’s I values for all cities home to a court that referred at least one preliminary reference concerning the free movement of goods and services.9

Figure 10: Spatial Autocorrelation of Free Movement of Goods and Services References, 1964-2013

9 Observations for Rome were dropped because of the sui generis nature of EU litigation before Italy’s supreme courts. Computing the Local Moran’s I requires one to specify a spatial relationship between the geo-referenced data points as well as a distance method; for the purposes of this analysis, the spatial relationship specified was “inverse distance,” and the distance method selected was the default “Euclidian distance.”

Recall from Figure 10 that free movement references appear to be clustered across northwest Italy, and particularly around the port-city of Genova. Indeed, Genova and the nearby city of Savona possess high and positive Z-scores, denoting that the litigation of EU free movement provisions is significantly higher across coastal Liguria than the surrounding regions. This is strong evidence of the presence of a “high- high” cluster. Similarly, this analysis reveals that the city of Venice possesses a low and negative Z-score, indicating the presence of a statistically significant “high-low” outlier. Overall, these analyses support the conclusion that the issue-specific litigation of EU law is capable of becoming spatially path-dependent.
Given the fact that the spatio-temporal structure of EU litigation across Italy tends to be issue- specific and spatially clustered, future research would benefit immensely by disaggregating the corpus of EU law by issue area and leveraging GIS technology to reach more nuanced conclusions regarding the responsiveness of the preliminary reference procedure to variant subnational socioeconomic conditions.

Conclusion

In this paper, we have taken a first step toward mapping EU law and uncovering the spatio-temporal structure of its judicial practice. We have demonstrated that attention to the spatial dimensions of EU law and governance can yield significant theoretical insights and challenge findings based on analyses that fail to take into account cross regional variations within member states. This line of analysis provides a much clearer picture than was previously available of how the reach of the EU’s legal system has developed over time. Furthermore,  we have demonstrated the plausibility of  using GIS technology to depict and analyze the spatial diffusion of EU law over time. To recapitulate, we show that although lower courts were the first Italian judicial institutions to refer cases to the ECJ, high courts have a substantially greater propensity to refer. Secondly, we demonstrate that population levels and domestic litigiousness  best explicate synchronic variation in Italian preliminary reference rates since 1997, and that there is evidence that the domestic litigation effect is causally heterogeneous. Finally, we provide strong evidence that EU litigation is both issue-specific and spatially clustered.
Although our empirical analysis is limited to the study of one legal mechanism (the preliminary ruling procedure) in one member state (Italy), this study opens the path to broad new avenues of research on the EU legal integration. In subsequent research, we will extend the analysis of the spatial diffusion of EU law to other member states and other measures of legal integration. Ultimately,  we  contend  that exploring the spatio-temporal dimensions of EU legal integration helps us move from the study of what Karl Llewellyn (1930) referred to as “paper laws” to the important ways in which EU legal provisions are invoked on the ground – in this case, quite literally.

Appendix

Appendix A: Proportion of Yearly Regional References Submitted by Court Type, 1964-2013

Appendix B: The Italian Judicial Hierarchy

Civil Courts	
Administrative  Courts	Constitutional Courts	

High Court (Final)	

Corte Suprema di Cassazione	Consiglio di Stato; Consiglio di giustizia amministrativa per la Regione Siciliana; Corte dei Conti; Commissione Tributaria  Centrale	

Corte  Costituzionale	

Mid-Level Court (Appeal)	Corte d'Appello; Corte d'Assise d'Appello	Commissione Tributaria di Secondo Grado (regionali); Corte dei Conti- Sezione Giurisdizionale  Regionale		

Low-Level Court (First Instance)	Tribunale; Landesgericht; Procura della Repubblica; Giudice di Pace; Giudice Conciliatore; Corte d'Assise; Pretura	
Tribunale  Amministrativo Regionale (TAR); Verwaltungsgericht; Commissione Tributaria di Primo Grado (comunali/proviciali)		

Appendix C: Population Change across Italy, 2001-2011

Appendix D: Litigation Before Northern and Southern Administrative Courts, 1997-2011

Appendix E: Distribution of Yearly Region-Level Preliminary References, 1964-2013

Appendix F: The Determinants of Region-Level Yearly Common Market References, 1997-2012

	1: Italy
DV: # Yearly Economic PRs	2: Italy (w/o Lazio)	3: North Italy	4: South Italy	
		DV: # Yearly Economic PRs	DV: # Yearly Economic PRs	DV: # Yearly Economic PRs	
Export Share	-0.0519**	-0.0140	-0.0220	0.473	
	(-2.32)	(-0.51)	(-0.29)	(0.91)	

ln(Population)	1.187****	1.248****	
0.332	1.828**	
	(5.05)	(5.32)	(1.31)	(2.41)	

Domestic Litigation	
0.0683**	
-0.0698	
0.465	
-0.284****	
	(2.24)	(-1.21)	(1.39)	(-3.37)	

Civic Participation	
0.00821	
0.0381	
0.0353	
-0.0997	
	(0.20)	(0.83)	(0.85)	(-0.42)	

Ln(GDP/capita)	2.202****	
0.255	
-3.421	
-2.176	
	(3.50)	(0.25)	(-1.41)	(-0.85)	
(Intercept)	-31.73****	-12.80	31.21	7.134	
	(-4.65)	(-1.29)	(1.22)	(0.26)	
N	218	207	87	88	
t statistics in parentheses
* p < 0.10,  ** p < 0.05,  *** p < 0.01,  **** p < 0.001
Note: Dependent variable is the number of yearly references at the regional level related to EU competition, taxation, free movement of goods and services, and establishment provisions.

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