The article is dedicated to the 100th anniversary of the first Slovenian National Government and the 100th anniversary of the Faculty of Law, University of Ljubljana. On 31 October 1918, the National Government in Ljubljana was appointed by the National Council of Slovenes, Croats and Serbs, the governing body of the newly created State of Slovenes, Croats and Serbs seated in Zagreb. The National Government had de facto administered the territory of the Austrian Province of Carniola and part of Styria until 1 December 1918, when the State of Slovenes, Croats and Serbs united with the Kingdom of Serbia into the newly created Kingdom of Serbs, Croats and Slovenes. The two centennials are closely related, as certain Faculty of Law Professors participated as delegates at the Paris Peace Conference in 1919–1920. The State of Slovenes, Croats and Serbs and the National Government in Ljubljana are first analysed from the international legal perspective. The State of Slovenes, Croats and Serbs fulfilled the criteria of a state under international law, although it was not recognised by the Allied and Associated Powers. On the other hand, the National Government did not meet such prerogatives. In addition, three articles, written by Professors Ivan Žolger, Ivan Tomšič, and Stanko Peterin are presented. These articles describe the existence of Yugoslavia from 1918 to 1992 and its transition from a unitary to a federal State. The process of the Yugoslav federation’s dissolution gave rise to the creation of the sovereign and independent Slovenia in 1991.