In Sorerejgntyin Cyberspace: Lex Lata Vel Non?, Michael Schmitt and Liis Vihul argue that territorial sovereignty is a primary rule of international law that limits cyber activities. They recognize, however, that not all cyber effects constitute violations of territorial sovereignty, and like Rule 4 in the Tallinn Manual 2.0 and its commentary, they acknowledge a distinct lack of consensus among the Tallinn participants on the critical question of applicable thresholds. Problematically, they do not identify the necessary state practice and opinio juris that would be required to establish either the primary rule that they proffer or the existence and contours of the exception they would recognize.
Gary Corn & Robert Taylor,
Concluding Observations on Sovereignty in Cyberspace,
Available at: https://digitalcommons.wcl.american.edu/facsch_lawrev/2166