This Volume XXIII of the the Italian Yearbook of International Law opens with a symposium on current trends and challenges of international investment law and arbitration taking into account the 2013 Tokyo Resolution of the Institut de droit international. It contains contributions on foreign investments, sovereignty and the public good (Francioni), on the role of customary law in investment regulation (Viñuales), on fragmentation (Petersmann), on a development-friendly definition of investment (Acconci), on the transfer provisions of Bilateral Investment Treaties (De Luca) and on the impact on foreign investments of EU law (Savarese, Rizzo) and of the Libyan conflict (Franceschelli).