Legal Interoperability: A Strategic Priority in Cyber Defence
Within NATO, interoperability is not limited to systems and platforms. Legal alignment across member nations is equally essential, especially in the cyber domain where ambiguity can hinder response, attribution, and operational coordination. The NATO-accredited Cooperative Cyber Defence Centre of Excellence, located in Estonia, has made legal interoperability one of its core areas of focus, alongside its broader mission of strengthening collective cyber resilience.
Through concept development, research, training, and exercises, the Centre supports NATO and Allied nations in navigating the legal complexities of cyberspace. Its work provides clarity in an area where consensus is growing but critical questions remain.
Shaping International Law for Cyberspace
While there is broad agreement that international law, including humanitarian law, applies in cyberspace, the application of these rules to cyber activities is still evolving. Nations are increasingly articulating their legal interpretations and national positions. These statements help promote a rules-based international order, but differences in interpretation can complicate joint operations and responses.
To address this challenge, the Centre has developed a number of legal resources that reflect practical experience and real-world cyber incidents. These tools support NATO’s operational planning and response frameworks, particularly in scenarios involving collective defence or attribution of cyber-attacks.
Practical Legal Tools for a Changing Digital Environment
Following the influential Tallinn Manuals, which convened international legal experts to analyze the application of international law to cyber operations, the Centre has continued its legal innovation by developing accessible and scenario-based tools for practitioners.
The Cyber Law Toolkit, launched in partnership with leading institutions including the University of Exeter, the Czech National Cyber and Information Security Agency and the International Committee of the Red Cross, is a web-based, interactive legal resource. It includes:
- Over 30 peer-reviewed cyber incident scenarios with detailed legal analysis
- A dynamic interactive web-based resource
- Authoritative references and explanations
- An expanding repository of national and international legal positions
In 2025, the Toolkit received the Jus Gentium Research Award from the American Society of International Law, recognizing its value as a practical guide for legal professionals working at the intersection of cyber operations and international law.
Supporting States in Clarifying National Legal Positions
Recognizing that many nations face challenges in articulating how international law applies to cyber activities, the Centre released the Handbook on Developing a National Position on International Law and Cyber Activities in May 2025. Developed in cooperation with the University of Exeter and the foreign ministries of Estonia and Japan, the handbook provides a structured framework to guide states through the process of forming clear, credible legal positions.
The handbook is the result of consultations with 46 nations and over 70 experts across four continents. It covers motivations for issuing national positions, methods of development, and best practices for presentation and communication. This resource equips national advisors and decision-makers with tools to participate confidently in legal and policy discussions on cyberspace governance.
From Legal Research to Operational Impact
Legal resources produced by the Centre are routinely referenced by NATO member states and international organizations. These materials also shape legal tracks within NATO’s largest cyber defence exercises, where participants from more than 40 countries must respond quickly and credibly to escalating scenarios. Exercises such as Locked Shields, Cyber Coalition, and others benefit directly from the Centre’s legal content.
These training environments provide feedback that informs future research and innovation, creating a continuous learning loop between legal theory and operational practice.
Enabling a Rules-Based and Credible Cyber Posture
The Tallinn Manuals, the Cyber Law Toolkit, and the National Positions Handbook are more than academic publications. They are catalysts for legal innovation, operational clarity, and collective accountability in the cyber domain. These efforts reinforce NATO’s legitimacy and leadership in global cyber governance, while supporting a stable and rules-based international environment.
Supporting NATO’s Cyber Transformation
As NATO’s hub for cyber defence expertise, the Cooperative Cyber Defence Centre of Excellence provides strategic, legal, operational, and technical support to the Alliance. Through its publications, partnerships, and training activities, the Centre strengthens collective understanding of the legal dimensions of cyber conflict and contributes directly to NATO’s transformation agenda.
Learn more by visiting the Centre’s website or following on Facebook, LinkedIn, X, or YouTube.
