Ketty Leyman v Institut national d'assurance maladie-invalidité (INAMI).
Date: 2009-10-01
18. As a preliminary point, it is appropriate to note that, although the questions referred by the national court make reference to Article 18 EC, a situation such as that in the main proceedings concerns Articles 39 EC and 42 EC.
19. It is apparent both from the order for reference and from the observations submitted to the Court that Ms Leyman moved to Luxembourg to take up employment there.
20. According to settled case-law, Article 18 EC, which sets out generally the right of every citizen of the Union to move and reside freely within the territory of the Member States, finds specific expression in Article 39 EC in relation to freedom of movement for workers (see Case C‑392/05 Alevizos  [2007] ECR I‑3505, paragraph 66, and Case C‑287/05 Hendrix  [2007] ECR I‑6909, paragraph 61).
40. As regards freedom of movement for workers, Article 42 EC leaves in being differences between the Member States’ social security systems and, consequently, in the rights of persons working in the Member States. It follows that substantive and procedural differences between the social security systems of individual Member States are unaffected by Article 42 EC (see Case C‑227/89 Rönfeldt  [1991] ECR I‑323, paragraph 12, and Case C‑165/91 van Munster  [1994] ECR I‑4661, paragraph 18).
41. It is not, however, in dispute that the aim of Article 39 EC would not be met if, through exercising their right to freedom of movement, migrant workers were to lose social security advantages guaranteed to them by the laws of a Member State. Such a consequence might discourage Community workers from exercising their right to freedom of movement and would therefore constitute an obstacle to that freedom (see Case C‑349/87 Paraschi  [1991] ECR I‑4501, paragraph 22, and van Munster , paragraph 27).
45. The Court has already held, in this respect, that the EC Treaty offers no guarantee to a worker that extending his activities into more than one Member State or transferring them to another Member State will be neutral as regards social security. Given the disparities in the social security legislation of the Member States, such an extension or transfer may be to the worker’s advantage in terms of social security or not, according to circumstance. It follows that, even where its application is less favourable, such legislation is still compatible with Articles 39 EC and 43 EC if it does not place the worker at a disadvantage as compared with those who pursue all their activities in the Member State where it applies or as compared with those who were already subject to it and if it does not simply result in the payment of social security contributions on which there is no return (see Joined Cases C‑393/99 and C‑394/99 Hervein and Others  [2002] ECR I‑2829, paragraph 51, and Case C‑493/04 Piatkowski  [2006] ECR I‑2369, paragraph 34).
48. In the present case, application of the national legislation at issue in the main proceedings to a migrant worker in the same way as to a non-migrant worker gives rise to unforeseen consequences, hardly compatible with the aim of Article 39 EC and attributable to the very fact that the migrant worker’s entitlement to invalidity benefits are governed by two different bodies of legislation, as is apparent from paragraphs 28 to 33 of this judgment (see, by analogy, van Munster , paragraph 30).
49. Where such a difference in legislation exists, the principle of cooperation in good faith laid down in Article 10 EC requires the competent authorities in the Member States to use all the means at their disposal to achieve the aim of Article 39 EC (see van Munster , paragraph 32).