(31)There is considerable legal uncertainty as to how far contracts concluded between entities in the public sector should be covered by public procurement rules. The relevant case-law of the Court of Justice of the European Union is interpreted differently between Member States and even between contracting authorities. It is therefore necessary to clarify in which cases contracts concluded within the public sector are not subject to the application of public procurement rules. Such clarification should be guided by the principles set out in the relevant case-law of the Court of Justice of the European Union. The sole fact that both parties to an agreement are themselves public authorities does not as such rule out the application of procurement rules. However, the application of public procurement rules should not interfere with the freedom of public authorities to perform the public service tasks conferred on them by using their own resources, which includes the possibility of cooperation with other public authorities. It should be ensured that any exempted public-public cooperation does not result in a distortion of competition in relation to private economic operators in so far as it places a private provider of services in a position of advantage vis-à-vis its competitors.