There is a general principle in international law that one state cannot take measures on the territory of another state by means of enforcement of national laws without the consent of the latter. It is possible--however--to observe a recent trend of a growing number of laws that aim to produce a legislative effect in third countries. The nature of the extraterritorial measures at stake and the interests involved have determined the intensity of protests against those measures, by businesses and legislators. This study explores the legal principles that sit behind extraterritoriality, and how such measures have come to be justified. It also examines how those enacting extraterritorial laws have sought to use mostly economic and diplomatic levers to seek compliance from third countries and entities registered in third countries. Finally, this study explores the impact extraterritoriality has had on the businesses and governments affected by it and outlines the defensive measures that can be taken to protect against the reach of such laws.