The paper is concerned with the role of national (domestic) legislation in the formation of investment regimes of the member countries of the Eurasian Economic Union. It is also discussed trends in the regulation of investment activity from the perspective of the regime approach and compares these trends with the development of domestic law and order. It is known that national legislation plays an essential role in establishing investment regimes, since the formulation of the internal framework governing investment activities is the competence of the State. It should also be noted that modern states establishing investment regimes consider several socio-economic and political factors, including competition in the global market. The member countries of the Eurasian Economic Union share a common historical background and maintain cooperative links with one another. Therefore, it is important for these countries to understand the legal environment of their partners for successful collaboration on investment projects.