The case concerned a preliminary reference from a Greek court in legal proceedings between the central Greek government and local authorities on the diversion of the river Acheloos in the north-west of Greece. The question arose whether the government measures leading to the partial diversion of the Acheloos river for water supply and electricity generation purposes was in conformity with a number of EU directives on water policy. Individuals may rely upon provisions of directives against a Member State because the CJEU considers it ‘unacceptable if a Member State were able to rely on their own failure to transpose directives correctly ‘so as to deprive individuals of the benefits of those rights stemming from the directive in question (vertical direct effect). However, a prerequisite to vertical direct effect is that the transposition period set in the directive has elapsed. The Greek authorities were required to adopt appropriate measures of conservation by carrying out river basin management plans. Greece had not adopted such river basin management plans at the time that the contested measures were taken, but the transposition deadline was after the adoption of the contested measures. Thus the Court considered that the project was not subject to article 4 of that directive, but the Greek authorities had to comply with the Inter-Environment Wallonie doctrine: the Greek authorities ‘had to refrain from taking any measures liable seriously to compromise the attainment of the result prescribed by Article 4 of that directive. The Court then went on to state that more public interests than the impossibility of satisfying drinking water, electricity production or irrigation of the receiving river basin could be capable of justifying the project under directive 2000/60 provided that the conditions of article 4 (7) were satisfied. Further on in the judgment, the Court answered the question whether under article 6 (4) of directive 92/43 irrigation and supply of drinking water constitute imperative reasons of overriding public interest that can justify the project impact on the integrity of the sites concerned. supply of drinking water is a consideration relating to human health is an imperative reason of overriding public interest, but, on the other hand, irrigation is only so to the extent that it may have beneficial consequences of primary importance for the environment. This was so because the directive is more protective of sites that host priority natural habitat type or a priority species.