Judges are increasingly asked to decide whether a rule of national law is applicable to a cyberspace actor who is not present in their jurisdiction, or whose activities do not clearly fall within the established understanding of the rule. They do this through interpreting the applicability and meaning of the law.
Every attempt to enforce a national law makes a claim that the law has authority over the cyberspace actor. By accepting that claim, the judge asserts that the law's claim is legitimate. This is a Hartian exercise, adopting the internal view of the national legal system as the test for legitimacy.
But in cyberspace the legitimacy of a national law claim is determined not by the internal perspective of the legal system but by the external perspective of cyberspace actors. A law will only have authority in cyberspace if it can convince cyberspace actors that its claim is legitimate. And a legal system which repeatedly makes illegitimate claims thereby weakens its status as a system which adheres to the rule of law.
Judges can help solve this problem by interpreting laws and applying public and private international law so as to reject applicability claims which are illegitimate. To do this successfully, they need to understand the jurisprudential foundations of any law's authority in cyberspace.