Terrorism, often specific to the area in which it occurs, is a special domain for the exercise of state sovereignty and, in this context, the comparative study of anti-terrorist legislation is a fruitful line of study. Can we combat a nationalist terrorism whose structures are founded on national historical and ideological roots, in the same way as international terrorism whose strength lies in the capacity of its perpetrators to have access to modern communication methods to convey their ideas and achieve their goals? And if and when several forms of terrorism emerge in the same territory, should we adopt different approaches according to the specific nature of the terrorism we wish to combat? .
It is the counter terrorism measures in which states decide to put in place on their territories which reflect the dominant characteristics of the phenomenon. The comparison between anti-terrorist systems of the Republic of Ireland and France is a good illustration of this: the former aims to fight an essentially separatist terrorism finding its expression in the activities of the Irish Republican Army (since, contrary to received ideas, the IRA is not only a terrorist organization specific to Northern Ireland) and the country is forced to combat all the forms of terrorism that exist (separatist, communist, internationalist or emanating from isolated groups). Obviously, it is not possible to respond in the same way to a group which, in spite of the acts of violence that it commits, has sympathy within public opinion and moreover has a recognized political wing, as to a range of highly active associations which have both national and international support and do not always openly state their claims.
However, there are common characteristics to all anti-terrorist legislation: fast-track procedures, extension of police powers, restriction of individual liberties, and the setting up of specialized courts to try the perpetrators of these acts of violence.