Terrorism is not a new phenomenon. During the last few centuries, humanity has witnessed several patterns of terrorism and the twentieth century added new patterns to terrorism.1 At the same time, the states of the world, individually as well as within the framework of international organisations, continue with various attempts to counter terrorism. As far as international law is concerned, an impressive expansion of positive law in the field of anti-terrorist legislation marked the twentieth century. The main producer of anti-terrorist legislation at the international level is the United Nations. Yet, this activity has not tackled such problems as the ambiguity of the definition of 'terrorism', the difference between a 'terrorist' and a 'freedom fighter' or between a 'terrorist organisation' and a 'national liberation movement', the balance between anti-terrorist policy and human rights, etc.