The last two decades have witnessed an exponential growth in debates on the use of foreign law by courts. Judges are said to increasingly rely on inspiration from outside of their national legal systems for solving purely domestic cases. This book puts similar claims to the test in relation to the highest national jurisdictions, i.e. supreme and constitutional courts, in Europe today. How often and why do judges choose to draw inspiration from foreign materials in solving domestic cases? The book addresses these questions from the empirical as well as the theoretical angle. Empirically, the genuine use of comparative arguments by the national highest courts in five European jurisdictions is examined: England and Wales, France, Germany, Czech Republic, and Slovakia. On the basis of comparative discussion of the practice and its national theoretical underpinning in these and partially also in other European systems, an overreaching theoretical framework for the current judicial use of comparative arguments is offered.