> the principle of legal certainty and the protection of legitimate expectations. These principles are derived from the provisions of the founding Treaties, and in particular from the ECJ’s decision-making practice. Although they do not use the list of legal principles underlying European law, it can be said that they represent a summary of what is fair, correct and proportionate. Legal certainty is so fundamental to the legal order that it is omnipresent in the law of the European Union. In practice, this principle implies several related, but not identical, principles that are regulated by the ECJ case law and secondary and primary law of the EU. Three main principles can be distinguished: European law should be clear and transparent; protect the legitimate expectations of participants in legal relationships; and retroactive legislation is admitted only exceptionally, for the existence of serious grounds, proper justification and protection of legitimate expectations. The principle of clarity and clarity of law derives, in particular, from ECJ case law and includes practical requirements such as making EU regulations specific and predictable, or implementing directives in a way that guarantees the clarity and clarity of the rights and obligations of individuals. The protection of legitimate expectations generally means that every person has the right to rely on such expectations aroused by an EU institution. Protection is provided to the extent that these expectations have been caused by the Union itself. The prohibition of retroactivity is basically similar to the protection of legitimate expectations. According to the case-law of the ECJ, it is admissible only if the objectives to be attained by the legislation in question are met, where the legitimate expectations of the parties concerned are protected and there is sufficient justification for the need to resort to retroactivity. it also requires that, in case of doubt, the rules are interpreted as if they did not have a retroactive effect. }