In migration studies, it is taken for granted that states do not only attempt to control overall numbers of immigrants, but also establish different regulatory regimes for refugees, labour migrants, family reunification, co-ethnics and many other categories of migrants. In studies of immigrant integration, however, most analyses have assumed that each state pursues a single and coherent national approach. The aim of this dissertation is to challenge this assumption by examining how states pursue integration differently for different categories of migrants in post-enlargement Europe. In addition to third country nationals I consider also migrants who have a special cultural and historical bond with their host countries, such as emigrants and descendants of emigrants or migrants from the former colonies (co-ethnics), as well as European Union citizens from old and new member states. The dissertation builds on empirical evidence collected from 1985 to 2012 at national, regional and city levels in two new countries of immigration in Western Europe: Italy and Spain. The first main finding is that both Italy and Spain chose to distance themselves from the integration policies of the more traditional countries of immigration in Europe, which they classify as failures. Instead, the new immigration countries searched for their "own" integration strategy, which they consider a token of sovereignty just as much as immigration control. Secondly, both states have introduced different integration policies and integration requirements for different categories of migrants. Rather than pursuing only one integration strategy, the states examined use their resources and abilities to simultaneously pursue different integration strategies for European citizens, co-ethnics and third country nationals. These strategies range from less to more restrictive (from laissez-faire to mandatory, sanction-based policies, such as the Italian integration agreement and language test). European Union citizens enjoy many rights in when residing in other member states without being included in their integration programmes, while third country nationals enjoy far fewer rights which they risk to lose if they do not comply with demanding integration programmes. Co-ethnics in turn are included in integration programmes but have more rights than other third country nationals and, in some areas such as access to citizenship and enrolment in the army, they have even more rights than European citizens. Finally, this dissertation finds a negative correlation between immigrants' social class in the host society and their rights and integration requirements: the lower the socio-economic position of the immigrant group, the fewer its rights and the more demanding the integration requirements it faces.