The article considers the views of the historian and jurist Sergey Andreevich Kotlyarevsky on the First State Duma of 1906 as the first legislative body of the people's representation, which marked the movement of the Russian Empire towards constitutional reforms. Through the prism of socio-political activity carried out by S.A. Kotlyarevsky, who was a deputy of the first Duma convocation and directly participated in the events preceding and accompanying its work, an important milestone in the history of the national state and law is highlighted. Being not only a scientist, but a practical ideologist as well, he developed the concept of the law-governed state, the provisions of which were reflected in the program statements of the Constitutional Democrats party, which became one of the active participants in the political processes of the period under review. It is noted that a progressive and obviously democratic nature of the scientist's views sound up-to-date in the principles of building the Russian state. One of them is the idea of universal suffrage and the party principle of building parliamentary representation. At this, it is pointed out that it is necessary to transform the state system in the key of reforming the political system, dialogue of forces and legal ways of resolving conflict issues. It is indicated that his views were developed on the basis of his personal experience of participation in the political events under consideration, in connection with which he gives a negative assessment to the work of the first Russian legislative body and erroneous positions of political parties. However, it was with the institution of parliamentarism, which had great potential for the peaceful transformation of the country, that the hopes and ideas of the scientist and socio-political figure about the embodiment of constitutionalism and the rule of law in Russia were connected.