The Political Geography of Legal IntegrationVisualizing Institutional Change in the European Union

I. Introduction

THE European Union is an exemplary case of political development through law. Advancing the rule of law is not just a normative aspiration for the EU; it is the EU’s primary mode of governance. Given its limited fiscal resources and the weakness of its administrative apparatus, the EU relies heavily on a judicialized mode of governance, enlisting private litigants to pursue its policy objectives and incorporating national courts into a pan-European judicial order.¹ In this light, while the EU is not a state in the traditional, coercive sense,² it can be conceptualized as a modern version of what medievalist historian Joseph Strayer called a “law-state”—a political order constructed principally through the progressive expansion of its judicial institutions.³

Importantly, the EU is not constructing its law-state on a tabula rasa, but on an institutional terrain populated by preexisting legal orders. In this respect, the EU’s experience has much in common with episodes of state building from late-medieval and early-modern Europe,⁴ to the nineteenth-century United States and other coming-together federations,⁵ or with the development of international regimes modeled on the EU like the Andean Community.⁶ In all these multilevel, multijurisdictional settings, those who would construct new, overarching judicial institutions work to reform and incorporate existing judicial institutions in the new legal order. These processes of institutional change occur incrementally through mechanisms identified by historical institutionalists, namely layering and conversion.⁷ New legal rules are layered atop existing ones, and at the same time those existing institutions are gradually converted to serve new purposes.

Building on this historical institutionalist perspective, this article explores how the EU’s legal order has developed and expanded over space and time. Over the past six decades, the architects of the EU legal order have layered new supranational institutions atop existing national legal orders while seeking to convert national judiciaries into EU courts. Specifically, we analyze how this process has been affected by its interaction with the preexisting judicial orders of its member states. In so doing, we show how these institutional developments not only have a temporal dimension that can be uncovered via time-series analysis, process tracing, and comparative historical analysis,⁸ but also have a spatial structure that can be visualized and analyzed through mapping.⁹ By theorizing and empirically evaluating the political geography of European legal integration, our approach demonstrates how scholars can literally “see” historical institutionalism at work.

Indeed, although the existing literature emphasizes that the EU judicial order is a key driver of European integration, it is less attentive to the political geography that underlies this process of institutional change. This spatiotemporal dimension matters because for the EU, as for any state or polity, the capacity to govern in practice depends on the geographical extent and temporal consistency with which it exercises authority across its territory. As Michael Mann puts it, the strength of a state depends on its infrastructural power: its institutional capability to exercise authority and implement policy throughout the territory it seeks to govern.¹⁰ For a political order like the EU that seeks to rule principally through law, spatiotemporal measures of the reach of the regime’s judicial authority arguably provide the best gauge of its infrastructural power.¹¹

In this vein, a powerful indicator of the reach of the EU’s judicial authority is an institutional mechanism known as the preliminary reference procedure.¹² The procedure empowers any national court to refer a question on the interpretation of EU law to the European Court of Justice (ecj) in Luxembourg,¹³ thereby serving as a transmission belt linking domestic courts with the ecj. Although formally all national judges are treaty-bound to respect the supremacy of EU law and are encouraged to solicit the interpretive authority of the ecj, use of the preliminary reference procedure signals where these European rules are actually being translated into concrete practice on the ground. When a national judge refers a lawsuit hinging on the application of...