Not All Those Who Wander (Over the Horizon) Are Lost: The Applicability of Existing Paradigms of International Law to Cyberspace and the Interpretation of Customary International Law

It may be considered banal at this point for a State to assert that ‘international law applies to cyberspace'. However, this belies tricky methodological questions regarding how a ‘new’ rule of customary international law (CIL) emerges. Cyberspace poses unique difficulties for the identification of CIL because of a paucity of publicly known State practice, vague statements, and attribution difficulties. However, this does not render CIL irrelevant to cyberspace. We argue that as the pace of technological development increases, interpretation of general rules of CIL may be used to ascertain their content when applied in cyberspace. First, the proposed interpretive method is discussed. Second, State practice on the application of sovereignty and jurisdiction in cyberspace are considered to demonstrate interpretation in practice, focusing on extraterritorial botnet takedowns. Third, objections to the interpretive method are considered but shown to be ultimately unsustainable. Normatively, the interpretation of CIL is an important tool for regulating cyberspace. First, it explains States' constant assertions that CIL applies to cyberspace despite the difficulties in meeting the usual tests. Second, on this approach, custom does not play catch-up to States' activities but develops contemporaneously. This allows international law to peer over the horizon and be better prepared to tackle future challenges.