The case of the inhabitants of the French colonies in 19th century shows the importance but also the insufficiency of legal assimilation for economic and social integration. The evolution of the legal statute of colored men, free, freed and slaves, reveals the assimilationnist or segregationist intent of the different regimes. The principle of colonization (preservation of the colonies, or even colonial expansion) was widely accepted in 19th century. It was not called into question, neither for the revolutionary period - then, the colonial question was only raised regarding the choice of the regime to apply to the colonies - nor during the second Republic. Parliamentary debates only started to examine the question after 1880, due to the colonial expansion. A study of the various statutes applied to the colonies, shows a constant principle : politicians always chose to keep the capacity to govern the colonies and their inhabitants without applying common law - except in 1795, however it was then more a matter of preserving the surface of the colonies - but by applying specific legislation or decrees. The proposed justification was the particular condition of the colonies which required specific legal rules. The metropolitan standards were only applied there if the acts mentioned it expressly. Legal assimilation should theoretically lead all colonies to be considered as true French departments. This is central to the unity and the indivisibility of the republic, which implies common law and institutions similar to those of the mother country. Throughout the evolution of the measures relating to the colonies, two elements persist : first, assimilationnist decrees were not always taken in the name of the equality and application of common law ; second, they did not result in a real economic and social integration. Does this result from a more or less explicit will of the successive governments to control the colonized rather than integrating them? Legal assimilation depended in fact on the judgement of the legislators evaluating the degree of attachment of the colonized to the metropolitan values. However, how could the inhabitants of the colonies adhere to the metropolitan laws while they did not have the means to be integrated economically and socially? Admittedly, legal assimilation was not sufficient for this integration, but was an essential precondition.