In the modern world, it is increasingly difficult for criminal law to be applied on a narrow territorial basis. This is especially apparent in the context of international fraud, drug smuggling, internet crime, and international terrorism. Against that background, this important new workexamines some fundamental, but hitherto neglected, issues of domestic criminal law. Where, and to whom, does that law apply? When, in particular, can national law properly concern itself with conduct that takes place wholly or partly abroad? Should it primarily be concerned with delinquent conduct,or with the consequences of that conduct, which may take effect in a different part of the world? On what basis can a person who is not a UK national be regarded as offending against the law if he is not within the territories governed by that law? What is the position under international law? Andhow are the precise boundaries (especially the adjacent maritime boundaries) of a nation's criminal law defined? The author examines the territorial and extraterritorial application of the criminal law, identifying many defects, lacunae and historical accidents; and considers possible ways in which some at least of the problems that beset these areas of law might be alleviated.