Yuji Iwasawa, Domestic Application of International Law: Focusing on Direct Applicability (Brill Nijhoff, 2023) Hardcover: 314 pp.

This book looks at the treatment of international law within domestic legal orders. It focuses on the concept of direct applicability and sorts out the confusion that arises from related terms, e.g., “domestic legal force,” “self-executing,” and “right of action.”

The author is a judge at the International Court of Justice and, before that, was Professor of Law at the University of Tokyo and Chair of the United Nations Human Rights Committee. As he notes in his Preface, the book builds upon his previous scholarship on the topic, inter alia, his 2002 Hague Academy lecture Domestic Application of International Law;¹ his book, published in Japanese, Domestic Applicability of Treaties: What Are “Self-Executing” Treaties?,² where he “attempted to reconstruct the theory of direct application and [propose] a renewed framework of analysis;”³ and a long line of journal articles and lectures.

The author builds upon the principle that a rule of international law has to have the force of law domestically (“domestic legal force”) before it can be applied without the need for further action by domestic authorities (“direct applicability”), but “[s]uch domestic legal force of international law is not a sufficient condition for its direct applicability.”⁴ Domestic legal force is a prerequisite but is in itself incomplete to enable direct applicability. In his approach, the presumption is that international law is directly applicable domestically provided there is no domestic law excluding it (“grounds to exclude”). The author also notes the need to examine the specific international obligation at stake, and determine whether it is sufficiently precise to be applied directly.

At the same time, the book looks at the confusion arising from the term “self-executing,” derived mainly from the U.S. concept of self-executing treaties, which has been interchangeably used with “direct effect,” the term favored by E.U. law, and “direct application.” These terms overlap with other notions, for instance, “invocability”⁵ and the question whether the obligation itself is by its nature merely programmatic or whether it can give rise to an actionable claim, or “transformation”⁶ and the question whether an international obligation either needs first to be transformed into domestic law, or whether it can be applied qua international law. The author points out that self-executing can be used both to denote international law rules that are “susceptible of being applied without the need of further measures,”⁷ whether executive or legislative, and likewise national law, e.g., constitutional provisions that on their own may be too broadly worded such that they can be applied only through further implementing measures.

The book develops these points in the key chapter entitled “Domestic Application of International Law: A Framework of Analysis,” where the author, having situated the debate in the context of various approaches and jurisdictions, then develops his theoretical framework, explaining why he prefers the term “direct applicability.” Those various contexts are covered in separate chapters. The books begins with the fully international approach comprising, first, the key relevant international decision (the Advisory Opinion of the Permanent Court of Justice in Jurisdiction of the Courts of Danzig⁸) and, in a later chapter, judgments by other international courts; and second, the main international human rights conventions and major multilateral treaties. It also situates the direct applicability concept in separate chapters on the law and practice of the United States and of the European Union. Finally, it extends the concept beyond treaty law and applies it to customary international law.

The strength of the book lies in its encompassing view of a subject that is usually examined from specific angles in national jurisdictions, and how it looks at the competing concepts in a wide range of contexts, e.g., in relation to international human rights instruments; within the U.S. and in E.U. member-states; and as regards not just treaty but likewise customary international law.

For instance, it examines the role of state intent and rejects that approach as “futile … because such an intention is either non-existent or unclear”⁹ in the text or travaux preparatoires of the various treaties examined in the book. It looks at the fundamental question of whether direct application is a problem only in dualist and not in monist states where it is a given, and concludes that this debate “has little bearing” even for states that, though dualist, have enabling constitutional clauses or “laws of approval,” referring to a legislative act whereby a state consents to a treaty and at the same time makes it directly applicable.¹⁰ Moreover, it asks whether the question of direct applicability arises only in treaties that create individual rights that give rise to a “right of action,” and concludes that a treaty can be directly applicable even when it does not create a cause of action for individuals. A treaty “does not by virtue of that fact alone establish a private right of action or confer [upon private individuals] a right to seek particular remedies such as damages.”¹¹ This discussion is most relevant to international human rights conventions, and carries special weight given that the author’s scholarship on this topic began with the domestic application of human rights treaties and considering the author’s work with the United Nations Human Rights Committee.

Finally, the book brings together in one volume an encyclopedic breadth of relevant material. For instance, on the issue whether direct application is determined by international law or by domestic law, the author combed through the opinions of various authors and publicists in a wide range of jurisdictions, and from classic to contemporary historical periods, including glossators who wrote in various languages in civil law traditions. The reader, by reading the book, is assured that he or she has at his disposal the full range of opinion on the matter.

The book is most timely. International law has increasingly governed not just the relations of states inter se but has reached into matters that erstwhile belonged to the domestic jurisdiction of states, pertaining to the rights of private individuals and, to complicate things further, in matters that traditionally belonged to the private sphere. It is in this historical and disciplinal context that we face the question of direct applicability. This phenomenon has manifested itself in many sub-fields of international law, e.g., sources of law, subjects of international law, state responsibility, and now, as the author deftly demonstrates, the direct application of both treaty and custom law, in its full doctrinal and normative implications.