As used in modern practice, judicial decisions, and literature, the term “countermeasures” covers the main part of the classical subject of “reprisals,” to which the first monographs of international law were devoted in the 14th century (B. de Sassoferrato and G. de Legnano). Two features used to be attached to countermeasures: (a) they are unilateral or individual measures adopted directly and independently by a state that takes the law into its own hands as based on the state’s “subjective” qualification of another state’s prior act as illegal (“self-help” or “self-protection”); (b) the measures would be essentially illegal if not for the fundamental prerequisite of the “objective” existence of a prior wrongful act committed by the state against which the countermeasures are adopted, and for the fulfillment of other requirements, substantive limits, and procedural conditions. In legal literature sometimes countermeasures not only include these measures but also those called “retorsion”: these are unfriendly and perhaps also retaliatory but not illegal irrespective of the conduct of the state these measures are taken against. The measures of retorsion have fallen outside the scope of the International Law Commission’s (ILC’s) work on international responsibility. On the other hand, countermeasures are not always differentiated from “sanctions” (or institutionalized coercive measures), and from unilateral measures to enforce “sanctions.” The development of judicial and institutional processes for furthering compliance and enforcement in general international law has not yet excluded such unsatisfactory legal remedies, as states’ practice and opinio juris (or the judicial decisions) prove. Legal scholars are also practically unanimous to recognize the admissibility of law enforcement through countermeasures, whether they consider it expressly or implicitly an exception or a right/faculty (or duty) of states. And so, this recognition is extended to international organizations. The ILC has taken note of all that, having contributed to the more precise development and definition of the countermeasures’ legal regime. The debates have been mainly on the conditions and restrictions to neutralize or reduce the risk of abuse, less on the pros and cons of the codification of that regime. Concerning the legality and legitimacy of countermeasures, there are other requirements related to, inter alia, their object (law-enforcement, not punishment), necessity and proportionality, temporary and reversible character, or the other obligations where fulfillment cannot be suspended as a countermeasure, all of them addressed by the ILC’s draft articles on responsibility. Alongside the recurrent renewal of the discussion relating to the illegality of reprisals/countermeasures involving the use of force, there are probably two other controversial issues, as highlighted during ILC’s work: the interrelationship between recourse to means of dispute settlement and to countermeasures and, in relation to erga omnes obligations and peremptory norms, the entitlement (right or duty) of noninjured states to adopt individual countermeasures. Although the term “countermeasure” has been used since at least 1923, as a general concept, referring to domains or disciplines with little or no relation to international law (medicine, materials or electromagnetic engineering, pollution prevention, defense and weapons), in recent years some practice and several academic writings attempt to adapt existing international law, including the law governing the self-help resources available to the victim states (self-defense, retaliation, regression, and the right to take countermeasures), from the kinetic (physical) space to a new one (“the fifth domain”), namely, the cyber domain.
Intrusion of international law into the national legal system