Free movement of workers within the European Economic Community. National rules making appointment to a certain job in a Member State conditional upon proof of an adequate knowledge of one of the official languages of that Member State.
Art. 48 EEC Treaty
Regulation (EEC) 1612/68 of the Council of 15 October 1968 on freedom of movement for workers within the Community
1. The EEC Treaty does not prohibit the adoption of a policy for the protection and promotion of a language of a Member State, provided that the implementation of such a policy does not encroach upon a fundamental freedom such as that of the free movement of workers. The requirements deriving from the measures aimed to implement such a policy must not in any circumstances be disproportionate in relation to the aim pursued and the manner in which they are applied must not bring about any discrimination against nationals of other Member States.
2. A permanent full-time post of lecturer in public vocational education institutions is a post of such a nature as to justify a requirement of linguistic knowledge, provided that the linguistic requirement in question is imposed as part of a policy for the promotion of the national language and provided that such requirement is applied in a proportionate and non-discriminatory manner.
(In the case at hand, the Irish Minister for Education refused to appoint a Netherlands national to a full-time post as an art teacher at the City of Dublin Vocational Education Committee, after she had failed a test intended to assess her knowledge of the Irish language).