21As regards more particularly the principle of proportionality, the Court has already held that, in accordance with that principle, the Member States must employ means which, whilst enabling them effectively to attain the objectives pursued by their domestic laws, cause the least possible detriment to the objectives and principles laid down by the relevant European Union legislation (see, inter alia, Case C-409/04Teleos and Others [2007] ECR I-7797, paragraph 52, and Netto Supermarkt, paragraph 19).