This chapter aims to use the notions ‘political crime’ and ‘political offence’ as synonyms. Both of these concepts have been widely employed in studies of politics and of law, regardless of the lack of definition for either. The chapter focuses on the changes in the way in which terrorism has been understood and dealt with in different times. It presents some of the most widely used definitions of terrorism as well as the problematic nature that lies in trying to create an internationally accepted definition. A growing number of crimes, including for instance attacks against the lives of heads of state, war crimes, genocide and finally terrorism, have been labelled as non-political. The political element has been acknowledged by the Global Terrorism database, which has gathered information on most international and domestic terrorist attacks since 1970.