While migration has always existed, and its consequences have always been important, few people have lived a mobile life in the history of mankind. Population immobility has recurrently been part and parcel of political strategies of social control and domination. Since the second half of the 20th century, however, the extent of geographical movements of individuals has expanded enormously. In particular, the size and scope of international travel has increased at an exponential pace. Favored by globalization and technological progress, transnationalism, initially linked to migration, has emerged as a relatively widespread phenomenon that involves a growing portion of the general population, especially, but not only, in developed countries. Mainly on the basis of research carried out in Europe, there is evidence that transnational practices tend to strengthen cosmopolitanism and the legitimacy of supranational polities (particularly the European Union [EU]), while it is less clear whether they entail denationalization. Further research is needed to improve the quality of independent and dependent variables in this area and assess the effect of international mobility and transnationalism outside the European context.
Political scientists use the concept of legitimacy to assess the rightfulness of political rule. Their research can approach legitimacy from two perspectives: When taking a normative approach, political scientists develop and justify their own evaluation of the rightfulness of political arrangements. When taking an empirical approach, they study how other people—such as political elites or citizens—evaluate the rightfulness of political rule. Both approaches have been used in research on the European Union. Scholarly discussions that approach the EU’s legitimacy from a normative perspective revolve around the question of which standards of rightfulness are appropriate for the EU. These depend largely on how the EU polity is conceptualized: as a technocratic regulatory agency, an intergovernmental organization, a federation, a demoi-cracy, or a system of multilevel governance. Since the EU is hybrid polity that possesses elements of each of these models, and is therefore difficult to classify, no consensus has emerged in this debate. Scholarship that approaches the EU’s legitimacy as an empirical phenomenon examines political attitudes and discourses in European society, asking whether, and why, societal actors treat the EU as legitimate. A diverse set of research methods—including public opinion surveys, content analysis of different kinds of texts, and qualitative interviews with citizens—have been applied to shed light on this question. While this research has not provided clear evidence of a “legitimacy crisis” of the EU, it does show that many Europeans relate to the EU with a sense of diffuse unease and skepticism, in part because they find it opaque and difficult to understand.