held that a State may not exercise its power in the territory of another State,5 while, in the Island of Palmas case, the Arbitral Tribunal stated as follows: "Sovereignty in the relations between States signifies independence. Independence in regard to a portion of the globe is the right to exercise therein, to the exclusion of any other State, the functions of a State."6 Taking these and other judgments into account, the Government of Japan considers that there exist certain forms of violation of sovereignty which may not necessarily constitute unlawful intervention prohibited under the principle of nonintervention. With respect to violation of sovereignty, the International Court of Justice (ICJ), in the Nicaragua case (1986), held that the United States had acted in breach of its obligation under customary international law not to intervene in the affairs of another State, and, in addition, that the United States, by directing or authorizing overflights of Nicaraguan territory, had acted in breach of its obligation under customary international law not to violate the sovereignty of another State.7 In addition, in the Costa Rica v. Nicaragua case (2015), the ICJ cited the absence of evidence that Costa Rica exercised authority on Nicaragua ’ s territory as the reason for dismissing Nicaragua's claim concerning the violation of its territorial integrity and sovereignty.8 Considering these cases, it can be presumed that, in some cases, a violation of sovereignty constitutes a violation of international law even when it does not fall within the scope of unlawful intervention. An act of causing physical damage or loss of functionality by means of cyber operations against critical infrastructure, including medical institutions, may constitute an unlawful intervention, depending on the circumstances, and at any rate, it may constitute a violation of sovereignty.9 As various opinions were expressed on the relationship between violation of sovereignty and unlawful intervention at the sixth GGE and the OEWG, it is desirable that a common understanding be forged through State practices and future discussions. (3) State responsibility Internationally wrongful acts committed by a State in cyberspace entail State responsibility. An internationally wrongful act occurs when the conduct of a State consisting of an action or omission violates an obligation prescribed by primary rules of international law. In the case of cyber operations as well, there is an internationally wrongful act when a State violates primary rules, including the principles of sovereignty, non-intervention, prohibition of the use of force, as well as various principles of 5 The Lotus case, PCIJ, Series A, No. 10, 1927, p. 18-19. Island of Palmas Case, Award, RIAA, Vol. II, p. 838. 7 Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America). Merits, Judgment. I.C.J. Reports 1986, p.136-139, paragraph 292. 8 Certain Activities Carried Out by Nicaragua in the Border Area (Costa Rica v. Nicaragua) and Construction of a Road in Costa Rica along the San Juan River (Nicaragua v. Costa Rica), Judgment, I.C.J. Reports 2015, p. 738, paragraph 223. 9 Tallinn Manual 2.0 also mentions physical damage to or loss of functionality of cyber infrastructure as a case that may constitute violation of sovereignty. 6 3