The Principle of Good Faith in International Law: Between Morality and Binding Force

The principle of good faith (bona fides) occupies an ambiguous but indispensable position in the architecture of international law. Rooted in Roman private law and moral philosophy, it has gradually migrated into the public international legal order, acquiring normative force through treaty codification, judicial pronouncements, and state practice. This article examines the doctrinal foundations of good faith, its expression in the jurisprudence of the International Court of Justice (ICJ), its structural role in the World Trade Organization (WTO) dispute settlement framework, and its contested application in international climate negotiations. The central analytical question is whether good faith constitutes a lex lata obligation capable of independent legal enforcement or whether it remains, at its core, a moral orientation that legal systems invoke instrumentally. The article argues that good faith occupies a hybrid normative position: it is simultaneously a customary international law norm of general application, a treaty-embedded standard of conduct, and a hermeneutic principle that disciplines legal interpretation; yet its enforceability is structurally contingent on context, institutional capacity, and the will of states to submit to adjudicative scrutiny.