According to art. 7 of the European Convention on Human Rights, "(1) No one shall be held guilty of any criminal offence on account of any act or omission which did not constitute a criminal offence under national or international law at the time when it was committed. Nor shall a heavier penalty be imposed than the one that was applicable at the time the criminal offence was committed. (2) This Article shall not prejudice the trial and punishment of any person for any act or omission which, at the time when it was committed, was criminal according to the general principles of law recognised by civilised nations." Being an expression of the nullum crimen sine lege, nulla poena sine lege principle, the rule established by art 7 is part of the so called "hard nucleus of law", jus cogens that cannot be infringed upon. The reason behind the principle of legality is that of removing arbitrariness from the system of law, thus making it compulsory in all democratic societies. Besides, the principle of legality is provisioned for by most legislations in one form or another. In the Romanian law, it is regulated through art. 12 of the Constitution, according to which no punishment may be established or applied other than in the conditions set out by the law and on the basis of the law as well as through art. 2 of the Criminal Code, according to which the law provisions which acts are crimes, the punishments applicable to criminals and the measures that can be taken in the case of the perpetration of such acts. The author shows that, most of the times, the principle of legality only refers to criminal matters. However, there are situations when the Court analyses this principle in causes of other nature than the criminal one, especially due to the fact that the notions that the Court uses have autonomous interpretation. In these cases, the Court finds that the principle provisioned by art. 7 is not applicable. Subsequently, the author analyses the requirements of the concept of predictability under the ECHR's view. The author shows that the Court operates with autonomous notions with regards to terms such as "crime", "law", "punishment" or "criminal matter", and even though the states are free to show which acts are crimes and which are not, the Court has reserved its right to analyse on its own whether a certain act sanctioned by the state is a crime under the meaning of art. 7 of the Convention. As a conclusion, the author shows that the notion of predictability is under continuous development. Ideally, all the criminal legal texts should be written in such a clear and precise manner that there are no interpretation and application issues. In reality, though, this is virtually impossible, and the Court's jurisprudence thus demands predictability. In the next section, the analysis is moved to the level of internal law, emphasising certain aspects from Romanian practice that have raised problems with regards to predictability. The discussion concentrates on the problem of the unconstitutionality of art. 74 Criminal Code, regarding the reparation of prejudice, text introduced in 2010 by the law regarding the Small Reform in Justice and declared unconstitutional by the Constitutional Court shortly thereafter. After that, the author verifies the incrimination found at art. 87 paragraph 1 of OUG 195/2002 regarding traffic on public roads, that of driving on public roads with a motor vehicle or tram while having alcoholic imbibition of over 0,80 g/l pure alcohol in blood. The author considers that there are certain deficiencies in the predictability of the text with regard to the border between contravention law and the criminal sphere and proposes, de lege ferenda, certain solutions. Finally, the author shows that, in his opinion, the requirement of predictability comes to cover the lack of clarity and precision of the criminal legal texts, seeing that in many situations there can be interpretation difficulties. Respecting the principle of the generality of law, a clear text is often difficult to obtain in the conditions of an abstract regulatory norm. On the other hand, a phrasing that is too rigid is to be avoided, as it may become an obstacle in the way of the development of law. The Court's jurisprudence demands predictability and it constantly provides new criteria regarding its incidence. Above these aspects, the importance of the concept of predictability derives from the fact that it offers new possibilities of applying fundamental principles of criminal law, especially that of legality provided by art. 7 of the Convention. [ABSTRACT FROM AUTHOR]