Over the past decade, the influence of translations of EUR-Lex legal douments on the original and translated Lithuanian administrative legal language had an impact on the decision of linguists and translation researchers to study the changing administrative Lithuanian language. The research object of this article is relative clauses which are specific to the French legal texts and which complement the subject content of the main sentence. In this article, the author examines the content of the above-mentioned relative clauses from the point of view of French interpretive translation theory and methodology. The author has an aim to identify the peculiarities of the use of relative clauses in French version of the opinions of the Advocate General of the Court of Justice of the European Union, and to describe translation solutions of the relative clauses into Lithuanian as well as genre characteristics of the translated texts. The study of the Advocate General’s opinions in the multilingual database of EUR-Lex documents reveals frequency of the relative clauses and peculiarities of their linking to the main sentence in the French legal texts. The results of the research reveal the new tendencies of the use of relative clauses in the administrative language different from those described in the scientific literature. The research of the translation of these sentences into Lithuanian indicated the frequency of translation solutions, the differential features of the translated legal language and the importance of translator's cognitive experience in the interpretation process of the content.