The wrongfulness of a cyber operation, which would otherwise constitute a breach of an international obligation of the responsible State, can be precluded if perpetrated in some specific circumstances. Such circumstances do not terminate or annul the international obligation, but justify or excuse the specific conduct. This chapter analyses the main circumstances precluding wrongfulness on the basis of the work of the International Law Commission. Hence, it focuses on consent, force majeure, distress and necessity. Force majeure, distress and necessity characterise situations in which a State is compelled to commit an act not compatible with its international obligations. The difference between force majeure and distress or necessity is the absence of the element of free choice in the former; while in case of distress or necessity, the State benefits from a certain degree of choice. Cyber operations conducted as a form of reprisal, either in self-defence or as countermeasures, will be dealt with in the last part of this book.