The provisions of the Agreement between the European Community and its Member States, of the one part, and the Swiss Confederation, of the other, on the free movement of persons concerning the equal treatment of employees must be interpreted as precluding the legislation of a Member State under which a resident national with unlimited liability to income tax who has exercised the right to freedom of movement in order to work as an employee on a part-time basis in the teaching profession for a legal person governed by public law established in Switzerland is denied a tax exemption in respect of the income from that employment, whereas such an exemption would be granted if that person had been so employed by a legal person governed by public law established in that Member State, in another Member State of the European Union or in another State to which the Agreement on the European Economic Area applies.

With regard to tax concessions, the principle of equal treatment, laid down in Article 9 of Annex I to the Agreement on the free movement of persons, may be relied on by a worker who is a national of a contracting party and has exercised his right to freedom of movement with regard to his State of origin. The legislation at issue treats resident taxpayers differently for tax purposes, depending on the source of their income. That different treatment is liable to deter such persons from exercising their right to freedom of movement and, therefore, constitutes unequal treatment, which is, in principle, contrary to Article 9(2) of Annex I to the Agreement.

Moreover, such different treatment cannot be justified by overriding reasons in the public interest. The Court has previously held, on the basis of considerations that may be applied to the present case, that different treatment as between natural persons exercising their right to freedom of movement by teaching part-time on a self-employed basis at a university established in another Member State, while at the same time living in their State of residence, and persons engaged in such activity in national territory cannot be justified by the public interest in the promotion of education, research and development, as such treatment infringes the freedom of teachers exercising their activity on a part-time basis to choose where within the European Union to provide their services, without it having been established that, in order to achieve the supposed objective of promoting education, it is necessary to limit the enjoyment of the tax exemption in question to those taxpayers engaged in similar activities in universities established on the territory of their Member State of residence.

Furthermore, any justification based on an overriding reason in the public interest connected with the need to safeguard the cohesion of the tax system in issue, in the absence of any direct link, from the point of view of the tax system, between the exemption from tax of expense allowances paid by national universities and an offsetting of that concession by a particular tax levy was similarly dismissed by the Court.

Lastly, the Court has held, first, that a tax concession of a general nature granted where an individual engages in activities of benefit to the general public is not a measure which concerns the content of teaching or the organisation of the education system. Second, when exercising their powers and discharging their responsibilities to organise their education systems, the Member States are bound, in any event, to comply with the Treaty provisions on freedom of movement. Accordingly, even if national legislation constituted a measure linked to the organisation of the education system, the fact remains that it is incompatible with the Treaty in so far as it influences the choice of persons teaching on a part-time basis with regard to the place in which they pursue that activity.

(see paras. 40, 43, 44, 50-54, 57, operative part)