The traditional and mainstream conception of international law presupposes a certain ideal type of State. However, each State is situated in a particular context – an Etat situé – and the universal, impartial and non-discriminatory application of international law to each State often produces unjustifiable results in the real world. International law thus needs to cope with this existential question in order to ensure and maintain the effectiveness of the international legal order, without, however, being trapped by a nihilistic relativism. This approach requires a flexible understanding and reconstruction of the international law-making theory. The present collection of essays gathers contributions written in honour of Professor Ryuichi Ida by his colleagues and former students, inspired by the dédicataire, who places particular emphasis upon the context, effectiveness and purposes of international law. The dédicataire’s perspective finds wide ranging applications and the present collection deals with international economic law, international criminal law, international environmental law, international law-making, the law of State responsibility and the law of international organizations. Contributors are: Tatsuya Abe, Pierre-Marie Dupuy, Shotaro Hamamoto, Machiko Kanetake, Tomohiko Kobayashi, Tomonori Mizushima, Hironobu Sakai, Akiho Shibata, Mari Takeuchi, Dai Tamada, Sakda Thanitcul, Zhi-an Wang, and Takuhei Yamada.