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From Grey Zone to
Customary International
Law: How Adopting the
Precautionary Principle
May Help Crystallize the
Due Diligence Principle in
Cyberspace
Abstract: The international principle of “due diligence” is well recognized under
international law, and is an outgrowth of the general obligation of States to “do no
harm”. The due diligence principle imposes an obligation on States to take afrmative
action to ensure their territory or objects over which they maintain sovereign control
are not used for internationally wrongful purposes. The due diligence principle has
been recognized by international scholars and jurists since the early 20th century, and
has been adopted as a principle of customary international law in the international
environmental law context by States and courts, including the International Court
of Justice. The International Court of Justice has specically endorsed a procedural
aspect of due diligence – that States must conduct environmental impact assessments,
where appropriate, as a precautionary measure to ensure their territory is not used for
internationally wrongful purposes. In 2013 and 2017, the Tallinn Manual and Tallinn
Manual 2.0 conrmed the due diligence principle applies in cyberspace. However,
in both manuals, the experts could not agree on the scope of its application. And, in
2017, the Tallinn Manual 2.0 experts agreed that the due diligence obligation does not
include a preventive feature, as is reected in international environmental law. This
paper examines this grey area of international law, and whether and to what extent the
Peter Z. Stockburger
Dentons US LLP
San Diego, California, USA
peter.stockburger@dentons.com
2018 10th International Conference on Cyber Conict
CyCon X: Maximising Eects
T. Minárik, R. Jakschis, L. Lindström (Eds.)
2018 © NATO CCD COE Publications, Tallinn
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