Data has become an object for governments all around the world to pursue. Those countries that can access, use and control data will be the rulers not only of the digital realm, but also of the real world. Cross-border flows of information and unlimited access to data are the main facilitators of the emerging digital economy. How easily data can be obtained, how expensive it is, and to what legal rules it must adapt are all critical questions for everyone involved, not least for data scientists. This chapter provides an overview of the measures to restrict the use of data put in place by various countries by adopting various legislative measures with the common characteristic of encumbering cross-border data transfers. This chapter furthermore looks into the drivers of these localisation measures and how these measures impact data science. The authors propose a policy framework for a balanced approach to data localisation, which takes into account the needs for data science.