Summary

International law prohibits states from using or supporting terrorism and requires them to take active anti-terrorist measures. The reality is not always as required. By violating these requirements, the state commits an internationally wrongful act and bears international responsibility to other countries. At the same time, practice shows that the official representatives of a country seldom commit terrorist acts: states usually use non-state actors for that purpose, with whom they do not have official relations. As international law imposes obligations related to terrorism above all on the state, it is essential to examine on what conditions the state concerned is responsible for the behaviour of non-state actors. The selection of measures taken against the state, including if it is justified to use armed forces as self-defence or within the framework of the collective security system, depends on whether the state is held responsible, i.e., the behaviour of non-state actors can be attributable to the state.

This article gives an overview of the nature of the responsibility of the state and then analyses on what conditions the state is responsible under international law for the behaviour of non-state terrorist actors. Special attention is paid to the allegation that the behaviour of such actors can be transferred to the state only provided that the latter offers them shelter.