Confidential Practice and International Law

Abstract This article explores the impact of secret State practice on the development and application of international law, particularly customary international law. It discusses the challenges of identifying customary international law when State conduct is confidential, especially in the fields of intelligence and national security. The author highlights that secrecy often stems from legitimate reasons, such as protecting sensitive information or national security concerns, but it can also hinder transparency and the evolution of international legal norms. Confidential practice cannot contribute to the creation and determination of customary international law unless disclosed to other States, as such knowledge is essential for States to react and form opinio juris . It is important to balance secrecy with transparency, and for States to publish their practice whenever possible to strengthen international law.