Niklas Luhmann’s theory of evolution is focused on the internal complexity of a system which brings a lot of varieties of possibilities into play, although it is capable of avoiding the idea of an external causation with the consequence of adaptation to innovation. Such an assumption would not be compatible with the construction of the autopoiesis of systems. Upon the basis of this idea, disruptive processes of societal transformation are also supposed to be unable to impede the construction and preservation of useful complexity. The article develops the argument that the distinction of a centre (court decisions) and a periphery (e. g., contracts) of the legal system is no longer plausible if the transformation of legal practices is taken into consideration. The increasing importance of the periphery compels us to observe the impact of practices on evolutionary processes which have not always already been anticipated by the system.