The present scientific paper is the fourth part and continuation of the in-depth scientific study of the developed system of engineering economic indicators, where the authors obtain results from the scientific research presented in a series of works on the development of the nanotechnologies and advanced materials industry in science and entrepreneurship in Latvia. Part Four determines the essential legal indicators of the development of nano-field at the macro, micro, and meso development levels of the economic environment in Latvia. The paper provides the interaction of new identified indicators of nano-field in terms of further scientific and practical activities. Latvia is analysed in comparison with other countries in the world.