This dissertation addresses some of the data protection challenges that have arisen from globalization, technological progress, terrorism and seamless cross-border flows of personal data. The focus of the thesis is to examine ways to protect the personal data of European citizens, which may be collected by communications service providers such as Google and Facebook, transferred to the US Government and data mined within the context of American national intelligence surveillance programs. The work explores the technology of data mining and examines whether there are sufficient guarantees under American law for the rights of non-US persons when it comes to applying this technology in the national-security context. Liane Colonna is a researcher at the Swedish Law and Informatics Research Institute (IRI). She is also a member of the New York Bar and holds a Master of Laws degree in European law from Stockholm University.