ENWhen evaluating compliance of a disputed piece of legislation with the Lithuanian Constitution, the Constitutional Court of the Republic of Lithuania often finds it to be in conflict not only with specific provisions of the Constitution but also with the constitutional principles of law. For the first time, the Constitutional Court did that in the 23 February 2000 ruling, where a contested regulation passed by the executive was found to be incompatible with both the constitutional provisions as well as the principle of the rule of law. That ruling was a point of reference, after which the constitutional principles evolved into a criterion of utmost importance in constitutional justice proceedings, a kind of a constitutional litmus test to evaluate contested legislation. An analysis of the case law of the Constitutional Court reveals that, since the above-mentioned ruling, constitutional justice cases where legal regulation is declared to be in conflict with the legal principles enshrined in the Constitution have been increasingly frequent. The official constitutional doctrine has gradually expanded the list of constitutional principles employed to examine the constitutionality of a piece of legislation and referenced, inter alia, in the operative part of the Court’s final acts. The author identified in the case law of the Constitutional Court and described the principles of constitutional law that served as a criterion for declaring the legal regulation as incompatible with the Constitution and specified in the operative parts of the Constitutional Court’s rulings adopted from 23 February 2000 to 31 August 2019. Namely, the principles of the rule of law, justice, sound governance, separation of powers, primacy of the Constitution and protection of legitimate expectations. [From the publication]