1. Enlargement means, in principle, an extension of the applicability of an agreement in terms of space. Primary and secondary European Union and European Community law become applicable within the territories of the new Member States. And it leads, at the same time, to an extension with regard to the personal scope of the already existing legal provisions. The citizens of the entering Member States become citizens of the European Union.9 Since European Community law grants individual rights to all citizens of the Union, these rights will consequently also protect the citizens of the new Member States.
2. The rules of the E.C. Treaty about free movement of workers (art. 39 E.C. Treaty) give workers with EU citizenship the right to take up employment in all Member States. Under Art. 49, 50 E.C. Treaty, provider of services are allowed to bring with them the workers necessary for the realization of their activity in another Member State.10 The requirement of a work permit, especially with the intention of protecting internal workers, or any other limitations of access to the labor market, are infringements of these rights. Infringements of that kind cannot be justified by referring to the ordre public, reasons of public security, or internal limitations drawn from Community constitutional law, because they are founded on economic reasons and possess discriminating character.11
3. Special forms of membership or the creation of a new space for integration in the sense of external differentiation, e.g. the concept of a Europe à deux vitesses, are still a topic of academic12 and sometimes political discussion but will presumably not have any impact on the present enlargement process. To a certain extent, possibilities of an internal differentiation are made possible by the Amsterdam Treaty under the provisions on closer cooperation.13 As far as the free movement of persons as a substantial part of the internal market is concerned, the preconditions required for the use of these provisions are rather strict.14 Thus, the mechanism of closer cooperation cannot be used to provide exceptions to the application of the basic freedoms in a legally admissible way.
9 See Art. 17 E.C. Treaty.
10 ECJ, case C-113/89, Rush Portuguesa,  ECR I-1417/12; case C-43/93, Vander Elst,  ECR I-3803/26.
11 See for details Becker, Freizügigkeit und Arbeitsmarktzugang in der EU, Diskussionspapiere zu Staat und Wirtschaft 15/2000, p. 16 et seq. with further references.
12 See for example Body, Europe of Many Circles (1990); Centre for Economic Policy Research, Flexible Integration - Towards a More Effective and Democratic Europe (1995).
13 See art. 11 E.C. Treaty and art. 43 - 45 E.U. Treaty. Becker, Differenzierungen der Rechtseinheit durch "abgestufte Integration", Beiheft 1 EuR (1998), p. 29, 47 et seq.; Chaltiel, Le Traité d'Amsterdam et la Coopération renforcée, RMU (1998), p. 289 et seq.; Ehlermann, Engere Zusammenarbeit nach dem Amsterdamer Vertrag: Ein neues Verfassungsprinzip?, EuR (1997), p. 362, 371 et seq.
14 The new provisions of the Treaty of Nice will leave more room for closer co-operation but not lead to a change in substance.