The thesis gives a brief introduction into the theoretical foundation of transnational criminal co-operation and the customary law status of "terrorism”. Within this contextual background the thesis analyses twelve of the 13 international counter-terrorism instruments currently in force and the legal mechanisms provided hereunder, as well as their application. It illustrates that all the agreed instruments adopted to date essentially follow the same structure, first established in the Hague Convention, requiring the criminalisation of specific conduct, establishing a clear basis of extra-territorial prescriptive and adjudicative jurisdiction under international law as well as providing associated obligations of co-operation in relation the prosecution of the alleged offender. The thesis analyses the inherent weaknesses of the established regime focusing inter alia on the common principle of aut dedere aut judicaré, the imperfection of the obligation to extradite, the normative status of the political offence exception and the influence of human rights principles. The study illustrates that although in formal terms the international accomplishments are considerable the analysed treaties have been inefficacious in obtaining their expressed aims of preventing and punishing international terrorism, and that their practical application has been negligible. The thesis, nevertheless, concludes that the established system represents the highest attainable level of international criminal co-operation since the lack of common values prevent more effective transnational co-operation.