44 the use of force acts of non-State actors, including individuals, organized groups, and terrorist organizations, unless they are attributable to a State pursuant to the law of State responsibility (Rule 6). In such a case, it would be the State, not the non-State actor, which is deemed to be in violation. The actions of non-State actors may be unlawful under international and domestic law, but not as a violation of the prohibition on the use of force. 6. The fact that a cyber operation does not rise to the level of a use of force does not necessarily render it lawful under international law. In particular, a cyber operation may constitute a violation of the prohibition on intervention. Although not expressly set out in the United Nations Charter, the prohibition of intervention is implicit in the principle of the sovereign equality of States laid out in Article 2(1) of the United Nations Charter. It is mentioned in a number of treaties and United Nations resolutions, the most signiﬁcant of which is the Declaration on Friendly Relations. According to the International Court of Justice, the principle is ‘part and parcel of customary international law’.4 7. The precise scope and content of the non-intervention principle remains the subject of some debate. In the Nicaragua case, the International Court of Justice held that ‘the principle forbids all States or groups of States to intervene directly or indirectly in the internal or external affairs of other States’.5 Therefore, ‘a prohibited intervention must accordingly be one bearing on matters in which each State is permitted, by the principle of State sovereignty, to decide freely. One of these is the choice of a political, economic, social and cultural system, and the formulation of foreign policy.’6 For instance, the Court held that supplying funds to insurgents was ‘undoubtedly an act of intervention in the internal affairs of Nicaragua’, although not a use of force.7 8. It is clear that not all cyber interference automatically violates the international law prohibition on intervention; ‘interference pure and simple is not intervention’.8 As noted by the Court in Nicaragua, ‘intervention is wrongful when it uses methods of coercion’.9 It follows that cyber espionage and cyber exploitation operations lacking a coercive element do not per se violate the non-intervention principle. Mere intrusion into another State’s systems does not violate the non-intervention 4 6 8 9 5 Nicaragua judgment, para. 202. Nicaragua judgment, para. 205. 7 Nicaragua judgment, para. 205. Nicaragua judgment, para. 228. I Oppenheim’s International Law: Peace 432 (Robert Jennings and Arthur Watts eds., 9th ed. 1992). Nicaragua judgment, para. 205.