Citizenship was introduced by the European Union Treaty (Consolidated Version of the Treaty on Functioning of the European Union  OJ C326/47). Article 20(1) intends to give the ordinary citizen a deeper and more tangible sense of belonging, in compliance with the fundamental aim of integration at the heart of the European Union (EU).
Citizenship encompasses the notion of uniting people by going beyond nationality in order to achieve peace, prosperity and solidarity (Schuman Declaration, 1950). However, there is an assertion in literature that citizenship is part of the emergence of a supranational state, thereby encroaching upon national sovereignty (Shaw 1997, p.4). Conversely, intergovernmentalists view Member States as playing a more prominent role within the Union, viewing them as the gatekeepers who ultimately possess power (Kostakopoulou 2007, p.626). Before examining these two conflicting views, this essay must first establish what the concept includes, and then examine its relationship with the Member States as exhibited in case law and portrayed throughout literature.
Historically, the market citizenship approach has prevailed. Consequently, Article 45 was interpreted narrowly, yet this reductionist view regarded individuals as merely economic actors, which effectively stripped them of identity and personality. Therefore, a rights-based approach has emerged as a critique - ‘the Migrant Worker is not to be viewed as a mere source of labour, but as a human being’ (Case 7/75 F v Belgian State  ECR 679). However, free movement is in clear conflict with the interests of Member States, which are keen to assert that the entry of individuals into their Community falls within their sovereign prerogative and often enact regulations to control levels of migration.
The introduction of citizenship was a significant step towards creating transnational solidarity by eliminating barriers to free movement. The four special rights conferred by the Union citizenship clearly attempt to fulfil this aim. However, the rights conferred are rather limited, partially diluting the revolutionary impact of such an introduction, compounded by the uncontroversial and nebulous nature of the provisions. It has been claimed that this is ‘a purely decorative and symbolic institution’ (Kostakopoulou 2007, p.623), arguably amounting to a mere codification of existing rights. Thus surely this empty concept poses little threat to national sovereignty as it is seemingly a label devoid of substance. Indeed, an intergovernmentalist perspective may advance the view that citizenship is ‘an example of pure symbolic gesture politics which does not actually strike at the heart of national sovereignty’ (Shaw 1997, p.3).
However, an analysis of the case law reveals that it is absurd to suggest that citizenship is merely decorative. One cannot escape the fact that ‘citizenship encompasses strengthened rights, with regard to free movement and residence and prohibition on discrimination on grounds of nationality…’ (Craig & De Búrca 2011, p.819). Despite the fact that competence as to nationality is ‘jealously guarded by Member States’, (O’Keeffe 1996, p.358) this has not prevented intervention by the ECJ (European Court of Justice). There have certainly been a number of cases in which the ECJ has challenged ‘core aspects of Member States’ migration policies’ (Craig & De Búrca 2011, p.832), as exhibited in Sala (C-85/96 Maria Martínez Sala v Freistaat Bayern  ECR I-2691). In this matter, the ECJ was willing to ‘explode the linkages’ (O’Leary, p.77) which had previously been required to apply the principle of non-discrimination Given the fact that they were EU citizens, they were entitled to equal access to social benefits available to nationals solely on basis of nationality (Craig & De Búrca, p.836). The ECJ has displayed a willingness to override the views of the Member States - in Grzelcyk (Case C-184/99 Rudy Grzelcykv CPAS  ECR I-6193). The influence of EU citizenship on the outcome of the case was once again crucial (Craig & De Búrca, p.837), and, most fundamentally, legal rights have been expanded even in the face of vocal Member State opposition (Craig & De Búrca, p.837).
Citizenship conveys notions of identity and Community belonging as it exhibits the notion of a political bond based on residence and transcending nationality completely. It is clear that many provisions are enacted with the aim to ‘facilitate their mobility within the Community’ (Case C-315/94 Peter de Vos v Stadt Bielefeld  ECR I-1417), subsequently regarding individuals as fully integrated into the fabric of society. Indeed, they are no longer regarded as aliens or guests, but are entitled to receive full equality of treatment (Case C-321/87 Commission v Belgium  ECR 997). Thus, despite the lack of the conferral of duties, EU citizenship still negatively impacts upon national sovereignty.
Nonetheless, there is a danger of overstating the impact that citizenship has had upon national sovereignty. Certainly, joining the EU implied a loss of sovereignty (Kostakopoulou, p.628), perhaps constituting ‘a novel and dangerous invasion by a Community institution of the sovereignty of the UK Parliament’ (Case C-213/89 Factortame I  ECR I-2433). But this was arguably ‘based on a misconception’ (Factortame) any limitation was ‘entirely voluntary’ (R v Secretary of State for Transport Ex p. Factortame Ltd (No.2)  1 AC 603) when the UK entered the EU when it passed the European Communities Act 1972. Supremacy ‘should by no means be confused with any kind of all-purpose subordination of member-state-law to Community law’ (MacCormick, p.117). Consequently, the general form of consent granted by the Member States when they joined the EU also entails consent to any provisions enacted thereafter, suggesting that the introduction of citizenship does not further impact upon national sovereignty. Perhaps there is even merit in the view that ‘nationality and citizenship complement one another. Without a common national identity, there is nothing to hold citizens together…’ (Miller, p.85). There is no reason why the two of them cannot co-exist, and provide a ‘shared platform’ in which individuals can assert their parallel identities (O’Keeffe, p.374). Perhaps EU citizenship is over-arching, but not necessarily intrusive upon Member States; it should be regarded as an invitation to join other networks (Preuss, p.280). This appears to recognise that citizenship should not seek to undermine, or to compromise attachment to an individual’s national state.
However, much of the threat to national sovereignty arguably lies not in what citizenship confers at the present moment, but in what it has the potential to. Perhaps the importance of citizenship lies in the fact that the first step has been taken (O’Keeffe, p.374). There are certainly two opposing paths that could be ventured – citizenship may either ‘remain what it actually appears to be, namely a terminological pooling of the few rights which the individual enjoys…’ (Preuss, p.268) or it ‘could ultimately even pave the way for the transition to a European Federal State’ (Preuss, p.268). While it may currently be difficult to discern which path will be taken, there is no doubt that citizenship has matured as an institution (Kostakopoulou, p.624), and is certainly ‘dynamic’ in nature (O’Keeffe, p.350).
To conclude, upon its introduction, many feared that citizenship would lead to a dilution of national sovereignty. Yet upon further examination, many have argued that the introduction of citizenship was purely symbolic, due to the absence of duties and the limited conferral of rights, therefore having very little impact on national sovereignty. However, the abundance of case law illustrates the importance of citizenship in its strengthening of rights, particularly with regards to free movement. It truly demonstrates a shift from citizens being regarded as economic actors to individuals with rights, ambitions and aspirations. In conferring such rights, the courts have often overridden the interests of Member States even in the face of strong vocal opposition (Craig & De Búrca, p.837). While ‘European citizenship was nothing more than a pale shadow’ (Kostakopoulou, p.625), arguably it is now emerging from the shadows, and posing a threat to national sovereignty. Moreover, its future may be uncertain, but it is clear that the evolution of citizenship, and thus the impact on the sovereignty of Member States cannot be underestimated. Many have confidently asserted the view that there is no doubt that this ‘embryonic concept’ (Lodge, p.380) will continue to grow.