41It also follows from settled case-law that Member States may adopt rules for the application of a regulation if they do not obstruct its direct applicability and do not conceal its Community nature, and if they specify that a discretion granted to them by that regulation is being exercised, provided that they adhere to the parameters laid down under it (Case C-113/02Commission v Netherlands [2004] ECR I-9707, paragraph 16 and the case-law cited).