The Legality of Espionage in Peacetime

Background: This research paper examines the legality of espionage during peacetime under the rules of international law. To address this issue, the paper focuses on several relevant international law rules, including the obligation to respect the sovereignty of other states and the prohibition on intervention. Although espionage is a longstanding instrument of statecraft essential for safeguarding national security, it occupies an uncertain legal position. International legal frameworks, including the UN Charter and customary international law, establish obligations such as the respect for state sovereignty and the prohibition of intervention, which espionage activities frequently challenge. The growth of modern surveillance capabilities, especially in the cyber domain, further complicates the legal and ethical boundaries of espionage. Methods: The study draws upon relevant international rules, such as the UN Charter and customary international law, as well as recent rulings by the International Court of Justice (ICJ) and the European Court of Human Rights (ECtHR), which can serve as a foundation for developing regulatory frameworks for espionage operations and surveillance activities. The study adopts a doctrinal legal research approach by systematically analysing primary sources of international law, including treaties, customary law principles, and jurisprudence from the ICJ and the ECtHR. It also incorporates a comparative review of state practice and relevant academic commentary to assess whether existing legal norms adequately regulate espionage activities during peacetime. Results and Conclusions: The findings indicate that espionage occupies a legally ambiguous space, particularly concerning the applicability of core principles of non-intervention and state sovereignty—especially in the cyber domain. In parallel, privacy has become enshrined in emerging human rights law, and legal safeguards around state surveillance have been introduced, emphasising proportionality, accountability, and supervision. Still, espionage operates in a highly nuanced legal and ethical territory that is neither wholly abhorrent nor entirely permissible. This contradiction reflects the ongoing tension between the challenges of balancing national security and the protection of individual rights. While espionage is widely acknowledged as vital to state security, international law does not explicitly ban it despite its potential to violate sovereignty and the principle of non-intervention. However, international law—through its emphasis on territorial integrity and sovereign equality—does not impose certain restraints on espionage activities. The study concludes that although espionage remains a multifaceted and indispensable component of state actions, it should not violate the principles and laws of sovereignty, human rights, or the broader framework of international law during peacetime. Legal and ethical ambiguity persists, necessitating the development of clearer regulatory frameworks that strike a balance between legitimate intelligence gathering and respect for sovereignty and individual rights. Ultimately, the research underscores that intelligence activities should not be permitted to undermine the stability of the international legal order or erode fundamental human rights protections.