1. For the fourth time in their history, the European Communities, now being part of the institutional framework of the European Union, have started an enlargement process. Several hopes and fears accompany this process, which is without precedent in terms of the number of states involved. On one hand, it is regarded as a "unique, historic task to further the integration of the continent by peaceful means."2 On the other hand, it will cause considerable costs and, some fear, a potential effect of destabilization. According to the Euro barometer of April 2001, the opinions are rather divided: 44% of EU citizens are in favor of enlargement but 35% are against it, and support levels vary significantly among the 15 Member States.3
Beyond doubt, there are various problems to be solved indeed. A major problem is the adaptation of the institutional architecture of the European Union, another the reform of the common agricultural policy. Other questions are still open for debate. One concern is the free movement of workers and, to a lesser degree, the free movement of services. Germany and Austria especially, the Member States sharing a common border with some states belonging to the candidates for accession, call for transitional measures in this respect.4 The Commission seems to be prepared to propose such arrangements within the accession negotiations.5
2. With respect to the present discussion on transitional measures for the free movement of persons, this paper aims to examine potential legal limits to amendments of the E.C. Treaty. As a starting point, I will show that the existing legal regime does not allow a non-application of the right to free movement on the basis of national citizenship, in other words, that there is not enough room for internal flexibility in this respect (infra, II.). Thus, external differentiation is needed. This leads to an overview of the transition regulations for accession until now (infra, III.). Next, I will answer the question what sort of transitional measures are admissible (infra, IV.) and investigate the limits existing for such measures (infra, V.). Finally, some short remarks will deal with the question whether the limits, assuming they were accepted, could be subject to judicial review (infra, VI.).
I should stress the fact that my observations are limited to answer legal questions of a more theoretical nature. I will not, despite their practical importance, deal with two other questions: (1) I will not debate the impact of migration on labor markets and social security in a welfare state in general6 and not try to assess the potential effects of Eastern enlargement on the situation in the Member States in particular.7 (2) I will leave aside the question whether more efficient measures to prevent negative effects of migration could be taken other than totally or partially inhibiting the free movement of workers.8
2 European Commission: European Union enlargement, A historic opportunity, http://europa.eu.int/comm/enlargement/docs/pdf/corpusen.pdf.
3 See Euro barometer Report No. 54, p. 82; http://europa.eu.int/comm/dg10/epo/eb/eb54/eb54_en.pdf.
4 See also for a more optimistic view: Eastern Enlargement to the EU: Economic Costs and Benefits for the EU Present Member States? Germany, Final Report on Study XIX/B1/9801, http://europa.eu.int/comm/budget/pdf/financementbudget/elargissement_etude/def_germany.pdf
5 See for different strategies European Commission, The Free Movement of Workers in the Context of Enlargement, Information note of 6.3.2001, http://europa.eu.int/comm/enlargement/docs/pdf/migration_enl.pdf.
6 See for example Simon, in: Giersch, Economic Aspects of Internationals Migration (1994), p. 231, 233; Poschner, Die Effekte der Migration auf die soziale Sicherung (1996); Michael/Hatzipanayotou, Welfare Effects of Migration in Societies with Indirect Taxes, Income Transfers and Public Good Provision, CES ifo Working Paper no. 347/2000.
7 See for the different estimates of potential migration European Commission, The Free Movement of Workers in the Context of Enlargement (note 5), Table 1.
8 Cf. Sinn et al., EU-Erweiterung und Arbeitskräftemigration: Wege zu einer schrittweisen Annäherung der Arbeitsmärkte (2000).