The so-called War on Terror may have begun on 11 September 2001, but terrorism has been practised for centuries. The international struggle against it started in the early part of the last century, and in 1937 the League of Nations concluded a Convention on the Prevention and Punishment of Terrorism. But a world war intervened and it never entered into force.

Terrorist crimes are ordinary crimes even if they are carried out for political, ideological or religious reasons, and so can be prosecuted where they are committed. However, once a criminal has fled abroad, extraditing him may not be easy, and if he cannot be extradited the state of refuge may not have jurisdiction over the crime. When the crime is committed abroad, the person's state of nationality would have to exercise extra-territorial jurisdiction in order to try him, although that is not usually possible for common law states. Nor do they normally assert criminal jurisdiction on the ground that one of their nationals was a victim. And it is unusual for states to have jurisdiction under their law over crimes committed abroad by foreign nationals against foreign nationals.