It emerges from the 'Les Verts' judgment that the action for annulment may lie against measures adopted by the European Parliament intended to have legal effects vis-à-vis third parties. This interpretation of Article 173 of the EEC Treaty (Article 230 of the EC Treaty) derives from the statement that 'the European Economic Community is a Community based on the rule of law, inasmuch as neither its Member States nor its institutions can avoid a review of the question whether the measures adopted by them are in conformity with the basic constitutional charter, the Treaty'.

Interactive diagram on the sources of European Union law, organised hierarchically in the form of a pyramid of rules, in which each subordinate rule must respect those rules above it. The Community legal order is distinguished by the autonomy of its sources and by the primacy of Community rules over national rules. (Situation before the entry into force of the Lisbon Treaty on 1 December 2009.)

Hierarchy of legal norms in the European Union after the entry into force of the Lisbon Treaty on 1 December 2009.

The Van Gend & Loos judgment is one of the most important judgments in the development of the Community legal order. The European Court of Justice specifies that the Community constitutes a new legal order of international law for the benefit of which the States have limited their sovereign rights and the subjects of which comprise not only Member States but also their nationals. The Court concludes from this a fundamental principle: that of the direct effect of Community law.

A fundamental judgment of the Court in respect of principles, the Costa v ENEL judgment shows that the EEC Treaty has created its own legal system which has become an integral part of the legal systems of the Member States, and that Community law takes precedence over national law.