52It follows that the provisions of Directive 1999/70, which implement the framework agreement, cannot, as such, be a source of obligations on the Council or the Commission in the exercise of their legislative or decision-making powers for the purposes of governing the relations between the European Communities and their staff. Nor can they, as such, justify a plea of illegality in respect of Article 88 of the CEOS or of the decision of 28 April 2004.