Events that took place on 9/11, when symbols of American nation were destroyed by hijacked civilian airplanes, raised the issue of the effectiveness of the currently existing legal framework which regulates terrorist activities. Prior to that event, dealing with terrorist activities was mostly regulated by conventions, many of which were ratified by no more than couple of states. However, it became questionable whether these instruments are sufficient to fight terrorists who are not only immune to a threat of sanctions, but are even ready to sacrifice their lives. After the attacks took place, the United States launched against Afghanistan an armed action, ending up in a more than a decade long occupation, holding Taliban regime responsible for the attacks undertaken by Al-Qaida. The United States response to the 9/11 raised an important question: what is the legal response to terrorist attacks? This article explores the current legal framework of the use of force in response to terrorist attacks, especially with regard to distinguishing terrorist acts which are attributable to a certain state, from those which are undertaken by a terrorist group, not associated with any particular state.