Part 1: All counter-terrorism policies elaborated in the aftermath of 11 September 2001 are characterised by the introduction of numerous exceptional measures, adopted on a temporary or even permanent basis, and by the strengthening of the international co-operation networks among the law enforcement agencies, the intelligence services and the judges. Relying on the assumption that some guarantees offered by the law with regard to civil rights and liberties are not compatible with an efficient fight against the new terrorist threat, exceptional measures are presented nowadays as absolutely necessary for the protection of the Western societies. Yet, the diffusion of this model of governance all over the Western countries has provoked numerous critics within both their political world and their civil societies. This paper aims therefore to analyse the public debate produced on that issue through the study of the media discourses held by the main supporters of the exceptionalism thesis and their rivals. The analysis will focus on the discourses held by politicians, experts and opinion leaders. It will seek to highlight the discursive mechanisms adopted in order to justify or to discredit the exceptionalism thesis. For this purpose, it will rely on the content analysis of the press discourses held in France, the United Kingdom, Italy and Greece since September 11, 2001. Part 2: Following the attacks of September 11 2001, many States whose France adopted a series of measurements to prevent and fight against the terrorist threats. Gradually, in the speeches as in the practices, these measures widened to include forms of dispute and spaces social for which they neither beforehand nor were officially intended. Then, in particular through the example of the antiglobalization movement, our study points how can this exception reinforce or on the contrary weaken the social cohesion? One can then put forth the assumption that this exception can be read within the meaning of illiberal practices exerted in a liberal mode in the name of the protection of freedoms. This hypothesis is based on the study of the adoption, in several European countries during last years, of multiple laws in various fields (internal security like LSQ and LSI in France, question of borders also). While being based on the study of the produced legislative texts, of the documents emanating of the antiglobalization movement and the discussions with various actors, the purpose of this research will be to study the antiglobalization movement with the prism of the exceptionnalism and social cohesion, while insisting more particularly on the emergence of new police practices and the apparition of attacks against the fundamental laws and public freedoms constitutive of the democracy. [ABSTRACT FROM AUTHOR]