To understand the emergence of an intergovernmental cooperation regarding justice and home affairs (JHA) within the EU, it is necessary to lead off from the problem of free movement of persons. It is indeed the perspective of the free movement of persons that raised the consciousness of European states on the necessity to cooperate in the fight against cross-border crime and illegal immigration. The Rome Treaty only planned for free movement of workers in an economic perspective and did not initially imply the generalised free movement of persons because that freedom was considered only in connection with an economic activity. Article 220 of the Rome Treaty already foresaw that MSs should, so far as is necessary, enter into negotiations with each other with a view to securing for the benefit of their nationals the simplification of formalities governing the reciprocal recognition and enforcement of judgments of courts or tribunals and of arbitration awards, which led to the adoption of the Brussels Agreement of 1978.