The article explores the birth of the Italian antitrust policy. After a brief explanation of the causes which prevented the approval of a national regulation until the 1990s, the work proves how the development of a European system of governance has been a basic factor to create a policy window inside the Italian policy system. The European level of governance acts as an independent variable in three ways: 1) agenda setting and policy timing; 2) normative spill-over; 3) policy core beliefs. Inside this framework the national actors partially re-shape the policy puzzle trying to reach their goals. In this process of policy change framed by the European Commission and the European Court of Justice the Italian political parties of the period 1988-1990 seemed to be unable to lead the change. Fragmented and divided, they didn't have a common set of values and beliefs to use as a tool for reducing the complexity of the transformation of the European governance. On the other hand some technicians and some specialized institutions seemed to have acted as an élite inside a more stable reformist coalition, promoting successfully the shift from a positive state to a regulatory state.